1================ 2Event Histograms 3================ 4 5Documentation written by Tom Zanussi 6 71. Introduction 8=============== 9 10 Histogram triggers are special event triggers that can be used to 11 aggregate trace event data into histograms. For information on 12 trace events and event triggers, see Documentation/trace/events.rst. 13 14 152. Histogram Trigger Command 16============================ 17 18 A histogram trigger command is an event trigger command that 19 aggregates event hits into a hash table keyed on one or more trace 20 event format fields (or stacktrace) and a set of running totals 21 derived from one or more trace event format fields and/or event 22 counts (hitcount). 23 24 The format of a hist trigger is as follows:: 25 26 hist:keys=<field1[,field2,...]>[:values=<field1[,field2,...]>] 27 [:sort=<field1[,field2,...]>][:size=#entries][:pause][:continue] 28 [:clear][:name=histname1][:<handler>.<action>] [if <filter>] 29 30 When a matching event is hit, an entry is added to a hash table 31 using the key(s) and value(s) named. Keys and values correspond to 32 fields in the event's format description. Values must correspond to 33 numeric fields - on an event hit, the value(s) will be added to a 34 sum kept for that field. The special string 'hitcount' can be used 35 in place of an explicit value field - this is simply a count of 36 event hits. If 'values' isn't specified, an implicit 'hitcount' 37 value will be automatically created and used as the only value. 38 Keys can be any field, or the special string 'stacktrace', which 39 will use the event's kernel stacktrace as the key. The keywords 40 'keys' or 'key' can be used to specify keys, and the keywords 41 'values', 'vals', or 'val' can be used to specify values. Compound 42 keys consisting of up to two fields can be specified by the 'keys' 43 keyword. Hashing a compound key produces a unique entry in the 44 table for each unique combination of component keys, and can be 45 useful for providing more fine-grained summaries of event data. 46 Additionally, sort keys consisting of up to two fields can be 47 specified by the 'sort' keyword. If more than one field is 48 specified, the result will be a 'sort within a sort': the first key 49 is taken to be the primary sort key and the second the secondary 50 key. If a hist trigger is given a name using the 'name' parameter, 51 its histogram data will be shared with other triggers of the same 52 name, and trigger hits will update this common data. Only triggers 53 with 'compatible' fields can be combined in this way; triggers are 54 'compatible' if the fields named in the trigger share the same 55 number and type of fields and those fields also have the same names. 56 Note that any two events always share the compatible 'hitcount' and 57 'stacktrace' fields and can therefore be combined using those 58 fields, however pointless that may be. 59 60 'hist' triggers add a 'hist' file to each event's subdirectory. 61 Reading the 'hist' file for the event will dump the hash table in 62 its entirety to stdout. If there are multiple hist triggers 63 attached to an event, there will be a table for each trigger in the 64 output. The table displayed for a named trigger will be the same as 65 any other instance having the same name. Each printed hash table 66 entry is a simple list of the keys and values comprising the entry; 67 keys are printed first and are delineated by curly braces, and are 68 followed by the set of value fields for the entry. By default, 69 numeric fields are displayed as base-10 integers. This can be 70 modified by appending any of the following modifiers to the field 71 name: 72 73 =========== ========================================== 74 .hex display a number as a hex value 75 .sym display an address as a symbol 76 .sym-offset display an address as a symbol and offset 77 .syscall display a syscall id as a system call name 78 .execname display a common_pid as a program name 79 .log2 display log2 value rather than raw number 80 .usecs display a common_timestamp in microseconds 81 =========== ========================================== 82 83 Note that in general the semantics of a given field aren't 84 interpreted when applying a modifier to it, but there are some 85 restrictions to be aware of in this regard: 86 87 - only the 'hex' modifier can be used for values (because values 88 are essentially sums, and the other modifiers don't make sense 89 in that context). 90 - the 'execname' modifier can only be used on a 'common_pid'. The 91 reason for this is that the execname is simply the 'comm' value 92 saved for the 'current' process when an event was triggered, 93 which is the same as the common_pid value saved by the event 94 tracing code. Trying to apply that comm value to other pid 95 values wouldn't be correct, and typically events that care save 96 pid-specific comm fields in the event itself. 97 98 A typical usage scenario would be the following to enable a hist 99 trigger, read its current contents, and then turn it off:: 100 101 # echo 'hist:keys=skbaddr.hex:vals=len' > \ 102 /sys/kernel/debug/tracing/events/net/netif_rx/trigger 103 104 # cat /sys/kernel/debug/tracing/events/net/netif_rx/hist 105 106 # echo '!hist:keys=skbaddr.hex:vals=len' > \ 107 /sys/kernel/debug/tracing/events/net/netif_rx/trigger 108 109 The trigger file itself can be read to show the details of the 110 currently attached hist trigger. This information is also displayed 111 at the top of the 'hist' file when read. 112 113 By default, the size of the hash table is 2048 entries. The 'size' 114 parameter can be used to specify more or fewer than that. The units 115 are in terms of hashtable entries - if a run uses more entries than 116 specified, the results will show the number of 'drops', the number 117 of hits that were ignored. The size should be a power of 2 between 118 128 and 131072 (any non- power-of-2 number specified will be rounded 119 up). 120 121 The 'sort' parameter can be used to specify a value field to sort 122 on. The default if unspecified is 'hitcount' and the default sort 123 order is 'ascending'. To sort in the opposite direction, append 124 .descending' to the sort key. 125 126 The 'pause' parameter can be used to pause an existing hist trigger 127 or to start a hist trigger but not log any events until told to do 128 so. 'continue' or 'cont' can be used to start or restart a paused 129 hist trigger. 130 131 The 'clear' parameter will clear the contents of a running hist 132 trigger and leave its current paused/active state. 133 134 Note that the 'pause', 'cont', and 'clear' parameters should be 135 applied using 'append' shell operator ('>>') if applied to an 136 existing trigger, rather than via the '>' operator, which will cause 137 the trigger to be removed through truncation. 138 139- enable_hist/disable_hist 140 141 The enable_hist and disable_hist triggers can be used to have one 142 event conditionally start and stop another event's already-attached 143 hist trigger. Any number of enable_hist and disable_hist triggers 144 can be attached to a given event, allowing that event to kick off 145 and stop aggregations on a host of other events. 146 147 The format is very similar to the enable/disable_event triggers:: 148 149 enable_hist:<system>:<event>[:count] 150 disable_hist:<system>:<event>[:count] 151 152 Instead of enabling or disabling the tracing of the target event 153 into the trace buffer as the enable/disable_event triggers do, the 154 enable/disable_hist triggers enable or disable the aggregation of 155 the target event into a hash table. 156 157 A typical usage scenario for the enable_hist/disable_hist triggers 158 would be to first set up a paused hist trigger on some event, 159 followed by an enable_hist/disable_hist pair that turns the hist 160 aggregation on and off when conditions of interest are hit:: 161 162 # echo 'hist:keys=skbaddr.hex:vals=len:pause' > \ 163 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 164 165 # echo 'enable_hist:net:netif_receive_skb if filename==/usr/bin/wget' > \ 166 /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger 167 168 # echo 'disable_hist:net:netif_receive_skb if comm==wget' > \ 169 /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger 170 171 The above sets up an initially paused hist trigger which is unpaused 172 and starts aggregating events when a given program is executed, and 173 which stops aggregating when the process exits and the hist trigger 174 is paused again. 175 176 The examples below provide a more concrete illustration of the 177 concepts and typical usage patterns discussed above. 178 179'special' event fields 180------------------------ 181 182 There are a number of 'special event fields' available for use as 183 keys or values in a hist trigger. These look like and behave as if 184 they were actual event fields, but aren't really part of the event's 185 field definition or format file. They are however available for any 186 event, and can be used anywhere an actual event field could be. 187 They are: 188 189 ====================== ==== ======================================= 190 common_timestamp u64 timestamp (from ring buffer) associated 191 with the event, in nanoseconds. May be 192 modified by .usecs to have timestamps 193 interpreted as microseconds. 194 cpu int the cpu on which the event occurred. 195 ====================== ==== ======================================= 196 197Extended error information 198-------------------------- 199 200 For some error conditions encountered when invoking a hist trigger 201 command, extended error information is available via the 202 corresponding event's 'hist' file. Reading the hist file after an 203 error will display more detailed information about what went wrong, 204 if information is available. This extended error information will 205 be available until the next hist trigger command for that event. 206 207 If available for a given error condition, the extended error 208 information and usage takes the following form:: 209 210 # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger 211 echo: write error: Invalid argument 212 213 # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist 214 ERROR: Couldn't yyy: zzz 215 Last command: xxx 216 2176.2 'hist' trigger examples 218--------------------------- 219 220 The first set of examples creates aggregations using the kmalloc 221 event. The fields that can be used for the hist trigger are listed 222 in the kmalloc event's format file:: 223 224 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/format 225 name: kmalloc 226 ID: 374 227 format: 228 field:unsigned short common_type; offset:0; size:2; signed:0; 229 field:unsigned char common_flags; offset:2; size:1; signed:0; 230 field:unsigned char common_preempt_count; offset:3; size:1; signed:0; 231 field:int common_pid; offset:4; size:4; signed:1; 232 233 field:unsigned long call_site; offset:8; size:8; signed:0; 234 field:const void * ptr; offset:16; size:8; signed:0; 235 field:size_t bytes_req; offset:24; size:8; signed:0; 236 field:size_t bytes_alloc; offset:32; size:8; signed:0; 237 field:gfp_t gfp_flags; offset:40; size:4; signed:0; 238 239 We'll start by creating a hist trigger that generates a simple table 240 that lists the total number of bytes requested for each function in 241 the kernel that made one or more calls to kmalloc:: 242 243 # echo 'hist:key=call_site:val=bytes_req' > \ 244 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 245 246 This tells the tracing system to create a 'hist' trigger using the 247 call_site field of the kmalloc event as the key for the table, which 248 just means that each unique call_site address will have an entry 249 created for it in the table. The 'val=bytes_req' parameter tells 250 the hist trigger that for each unique entry (call_site) in the 251 table, it should keep a running total of the number of bytes 252 requested by that call_site. 253 254 We'll let it run for awhile and then dump the contents of the 'hist' 255 file in the kmalloc event's subdirectory (for readability, a number 256 of entries have been omitted):: 257 258 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist 259 # trigger info: hist:keys=call_site:vals=bytes_req:sort=hitcount:size=2048 [active] 260 261 { call_site: 18446744072106379007 } hitcount: 1 bytes_req: 176 262 { call_site: 18446744071579557049 } hitcount: 1 bytes_req: 1024 263 { call_site: 18446744071580608289 } hitcount: 1 bytes_req: 16384 264 { call_site: 18446744071581827654 } hitcount: 1 bytes_req: 24 265 { call_site: 18446744071580700980 } hitcount: 1 bytes_req: 8 266 { call_site: 18446744071579359876 } hitcount: 1 bytes_req: 152 267 { call_site: 18446744071580795365 } hitcount: 3 bytes_req: 144 268 { call_site: 18446744071581303129 } hitcount: 3 bytes_req: 144 269 { call_site: 18446744071580713234 } hitcount: 4 bytes_req: 2560 270 { call_site: 18446744071580933750 } hitcount: 4 bytes_req: 736 271 . 272 . 273 . 274 { call_site: 18446744072106047046 } hitcount: 69 bytes_req: 5576 275 { call_site: 18446744071582116407 } hitcount: 73 bytes_req: 2336 276 { call_site: 18446744072106054684 } hitcount: 136 bytes_req: 140504 277 { call_site: 18446744072106224230 } hitcount: 136 bytes_req: 19584 278 { call_site: 18446744072106078074 } hitcount: 153 bytes_req: 2448 279 { call_site: 18446744072106062406 } hitcount: 153 bytes_req: 36720 280 { call_site: 18446744071582507929 } hitcount: 153 bytes_req: 37088 281 { call_site: 18446744072102520590 } hitcount: 273 bytes_req: 10920 282 { call_site: 18446744071582143559 } hitcount: 358 bytes_req: 716 283 { call_site: 18446744072106465852 } hitcount: 417 bytes_req: 56712 284 { call_site: 18446744072102523378 } hitcount: 485 bytes_req: 27160 285 { call_site: 18446744072099568646 } hitcount: 1676 bytes_req: 33520 286 287 Totals: 288 Hits: 4610 289 Entries: 45 290 Dropped: 0 291 292 The output displays a line for each entry, beginning with the key 293 specified in the trigger, followed by the value(s) also specified in 294 the trigger. At the beginning of the output is a line that displays 295 the trigger info, which can also be displayed by reading the 296 'trigger' file:: 297 298 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 299 hist:keys=call_site:vals=bytes_req:sort=hitcount:size=2048 [active] 300 301 At the end of the output are a few lines that display the overall 302 totals for the run. The 'Hits' field shows the total number of 303 times the event trigger was hit, the 'Entries' field shows the total 304 number of used entries in the hash table, and the 'Dropped' field 305 shows the number of hits that were dropped because the number of 306 used entries for the run exceeded the maximum number of entries 307 allowed for the table (normally 0, but if not a hint that you may 308 want to increase the size of the table using the 'size' parameter). 309 310 Notice in the above output that there's an extra field, 'hitcount', 311 which wasn't specified in the trigger. Also notice that in the 312 trigger info output, there's a parameter, 'sort=hitcount', which 313 wasn't specified in the trigger either. The reason for that is that 314 every trigger implicitly keeps a count of the total number of hits 315 attributed to a given entry, called the 'hitcount'. That hitcount 316 information is explicitly displayed in the output, and in the 317 absence of a user-specified sort parameter, is used as the default 318 sort field. 319 320 The value 'hitcount' can be used in place of an explicit value in 321 the 'values' parameter if you don't really need to have any 322 particular field summed and are mainly interested in hit 323 frequencies. 324 325 To turn the hist trigger off, simply call up the trigger in the 326 command history and re-execute it with a '!' prepended:: 327 328 # echo '!hist:key=call_site:val=bytes_req' > \ 329 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 330 331 Finally, notice that the call_site as displayed in the output above 332 isn't really very useful. It's an address, but normally addresses 333 are displayed in hex. To have a numeric field displayed as a hex 334 value, simply append '.hex' to the field name in the trigger:: 335 336 # echo 'hist:key=call_site.hex:val=bytes_req' > \ 337 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 338 339 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist 340 # trigger info: hist:keys=call_site.hex:vals=bytes_req:sort=hitcount:size=2048 [active] 341 342 { call_site: ffffffffa026b291 } hitcount: 1 bytes_req: 433 343 { call_site: ffffffffa07186ff } hitcount: 1 bytes_req: 176 344 { call_site: ffffffff811ae721 } hitcount: 1 bytes_req: 16384 345 { call_site: ffffffff811c5134 } hitcount: 1 bytes_req: 8 346 { call_site: ffffffffa04a9ebb } hitcount: 1 bytes_req: 511 347 { call_site: ffffffff8122e0a6 } hitcount: 1 bytes_req: 12 348 { call_site: ffffffff8107da84 } hitcount: 1 bytes_req: 152 349 { call_site: ffffffff812d8246 } hitcount: 1 bytes_req: 24 350 { call_site: ffffffff811dc1e5 } hitcount: 3 bytes_req: 144 351 { call_site: ffffffffa02515e8 } hitcount: 3 bytes_req: 648 352 { call_site: ffffffff81258159 } hitcount: 3 bytes_req: 144 353 { call_site: ffffffff811c80f4 } hitcount: 4 bytes_req: 544 354 . 355 . 356 . 357 { call_site: ffffffffa06c7646 } hitcount: 106 bytes_req: 8024 358 { call_site: ffffffffa06cb246 } hitcount: 132 bytes_req: 31680 359 { call_site: ffffffffa06cef7a } hitcount: 132 bytes_req: 2112 360 { call_site: ffffffff8137e399 } hitcount: 132 bytes_req: 23232 361 { call_site: ffffffffa06c941c } hitcount: 185 bytes_req: 171360 362 { call_site: ffffffffa06f2a66 } hitcount: 185 bytes_req: 26640 363 { call_site: ffffffffa036a70e } hitcount: 265 bytes_req: 10600 364 { call_site: ffffffff81325447 } hitcount: 292 bytes_req: 584 365 { call_site: ffffffffa072da3c } hitcount: 446 bytes_req: 60656 366 { call_site: ffffffffa036b1f2 } hitcount: 526 bytes_req: 29456 367 { call_site: ffffffffa0099c06 } hitcount: 1780 bytes_req: 35600 368 369 Totals: 370 Hits: 4775 371 Entries: 46 372 Dropped: 0 373 374 Even that's only marginally more useful - while hex values do look 375 more like addresses, what users are typically more interested in 376 when looking at text addresses are the corresponding symbols 377 instead. To have an address displayed as symbolic value instead, 378 simply append '.sym' or '.sym-offset' to the field name in the 379 trigger:: 380 381 # echo 'hist:key=call_site.sym:val=bytes_req' > \ 382 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 383 384 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist 385 # trigger info: hist:keys=call_site.sym:vals=bytes_req:sort=hitcount:size=2048 [active] 386 387 { call_site: [ffffffff810adcb9] syslog_print_all } hitcount: 1 bytes_req: 1024 388 { call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8 389 { call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7 390 { call_site: [ffffffff8154acbe] usb_alloc_urb } hitcount: 1 bytes_req: 192 391 { call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7 392 { call_site: [ffffffff811e3a25] __seq_open_private } hitcount: 1 bytes_req: 40 393 { call_site: [ffffffff8109524a] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 394 { call_site: [ffffffff811febd5] fsnotify_alloc_group } hitcount: 2 bytes_req: 528 395 { call_site: [ffffffff81440f58] __tty_buffer_request_room } hitcount: 2 bytes_req: 2624 396 { call_site: [ffffffff81200ba6] inotify_new_group } hitcount: 2 bytes_req: 96 397 { call_site: [ffffffffa05e19af] ieee80211_start_tx_ba_session [mac80211] } hitcount: 2 bytes_req: 464 398 { call_site: [ffffffff81672406] tcp_get_metrics } hitcount: 2 bytes_req: 304 399 { call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 400 { call_site: [ffffffff81089b05] sched_create_group } hitcount: 2 bytes_req: 1424 401 . 402 . 403 . 404 { call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 1185 bytes_req: 123240 405 { call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl [drm] } hitcount: 1185 bytes_req: 104280 406 { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 1402 bytes_req: 190672 407 { call_site: [ffffffff812891ca] ext4_find_extent } hitcount: 1518 bytes_req: 146208 408 { call_site: [ffffffffa029070e] drm_vma_node_allow [drm] } hitcount: 1746 bytes_req: 69840 409 { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 2021 bytes_req: 792312 410 { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 2592 bytes_req: 145152 411 { call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 2629 bytes_req: 378576 412 { call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 2629 bytes_req: 3783248 413 { call_site: [ffffffff81325607] apparmor_file_alloc_security } hitcount: 5192 bytes_req: 10384 414 { call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 5529 bytes_req: 110584 415 { call_site: [ffffffff8131ebf7] aa_alloc_task_context } hitcount: 21943 bytes_req: 702176 416 { call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 55759 bytes_req: 5074265 417 418 Totals: 419 Hits: 109928 420 Entries: 71 421 Dropped: 0 422 423 Because the default sort key above is 'hitcount', the above shows a 424 the list of call_sites by increasing hitcount, so that at the bottom 425 we see the functions that made the most kmalloc calls during the 426 run. If instead we we wanted to see the top kmalloc callers in 427 terms of the number of bytes requested rather than the number of 428 calls, and we wanted the top caller to appear at the top, we can use 429 the 'sort' parameter, along with the 'descending' modifier:: 430 431 # echo 'hist:key=call_site.sym:val=bytes_req:sort=bytes_req.descending' > \ 432 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 433 434 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist 435 # trigger info: hist:keys=call_site.sym:vals=bytes_req:sort=bytes_req.descending:size=2048 [active] 436 437 { call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 2186 bytes_req: 3397464 438 { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 1790 bytes_req: 712176 439 { call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 8132 bytes_req: 513135 440 { call_site: [ffffffff811e2a1b] seq_buf_alloc } hitcount: 106 bytes_req: 440128 441 { call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 2186 bytes_req: 314784 442 { call_site: [ffffffff812891ca] ext4_find_extent } hitcount: 2174 bytes_req: 208992 443 { call_site: [ffffffff811ae8e1] __kmalloc } hitcount: 8 bytes_req: 131072 444 { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 859 bytes_req: 116824 445 { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 1834 bytes_req: 102704 446 { call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 972 bytes_req: 101088 447 { call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl [drm] } hitcount: 972 bytes_req: 85536 448 { call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 3333 bytes_req: 66664 449 { call_site: [ffffffff8137e559] sg_kmalloc } hitcount: 209 bytes_req: 61632 450 . 451 . 452 . 453 { call_site: [ffffffff81095225] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 454 { call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 455 { call_site: [ffffffff812d8406] copy_semundo } hitcount: 2 bytes_req: 48 456 { call_site: [ffffffff81200ba6] inotify_new_group } hitcount: 1 bytes_req: 48 457 { call_site: [ffffffffa027121a] drm_getmagic [drm] } hitcount: 1 bytes_req: 48 458 { call_site: [ffffffff811e3a25] __seq_open_private } hitcount: 1 bytes_req: 40 459 { call_site: [ffffffff811c52f4] bprm_change_interp } hitcount: 2 bytes_req: 16 460 { call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8 461 { call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7 462 { call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7 463 464 Totals: 465 Hits: 32133 466 Entries: 81 467 Dropped: 0 468 469 To display the offset and size information in addition to the symbol 470 name, just use 'sym-offset' instead:: 471 472 # echo 'hist:key=call_site.sym-offset:val=bytes_req:sort=bytes_req.descending' > \ 473 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 474 475 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist 476 # trigger info: hist:keys=call_site.sym-offset:vals=bytes_req:sort=bytes_req.descending:size=2048 [active] 477 478 { call_site: [ffffffffa046041c] i915_gem_execbuffer2+0x6c/0x2c0 [i915] } hitcount: 4569 bytes_req: 3163720 479 { call_site: [ffffffffa0489a66] intel_ring_begin+0xc6/0x1f0 [i915] } hitcount: 4569 bytes_req: 657936 480 { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23+0x694/0x1020 [i915] } hitcount: 1519 bytes_req: 472936 481 { call_site: [ffffffffa045e646] i915_gem_do_execbuffer.isra.23+0x516/0x1020 [i915] } hitcount: 3050 bytes_req: 211832 482 { call_site: [ffffffff811e2a1b] seq_buf_alloc+0x1b/0x50 } hitcount: 34 bytes_req: 148384 483 { call_site: [ffffffffa04a580c] intel_crtc_page_flip+0xbc/0x870 [i915] } hitcount: 1385 bytes_req: 144040 484 { call_site: [ffffffff811ae8e1] __kmalloc+0x191/0x1b0 } hitcount: 8 bytes_req: 131072 485 { call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl+0x282/0x360 [drm] } hitcount: 1385 bytes_req: 121880 486 { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc+0x32/0x100 [drm] } hitcount: 1848 bytes_req: 103488 487 { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state+0x2c/0xa0 [i915] } hitcount: 461 bytes_req: 62696 488 { call_site: [ffffffffa029070e] drm_vma_node_allow+0x2e/0xd0 [drm] } hitcount: 1541 bytes_req: 61640 489 { call_site: [ffffffff815f8d7b] sk_prot_alloc+0xcb/0x1b0 } hitcount: 57 bytes_req: 57456 490 . 491 . 492 . 493 { call_site: [ffffffff8109524a] alloc_fair_sched_group+0x5a/0x1a0 } hitcount: 2 bytes_req: 128 494 { call_site: [ffffffffa027b921] drm_vm_open_locked+0x31/0xa0 [drm] } hitcount: 3 bytes_req: 96 495 { call_site: [ffffffff8122e266] proc_self_follow_link+0x76/0xb0 } hitcount: 8 bytes_req: 96 496 { call_site: [ffffffff81213e80] load_elf_binary+0x240/0x1650 } hitcount: 3 bytes_req: 84 497 { call_site: [ffffffff8154bc62] usb_control_msg+0x42/0x110 } hitcount: 1 bytes_req: 8 498 { call_site: [ffffffffa00bf6fe] hidraw_send_report+0x7e/0x1a0 [hid] } hitcount: 1 bytes_req: 7 499 { call_site: [ffffffffa00bf1ca] hidraw_report_event+0x8a/0x120 [hid] } hitcount: 1 bytes_req: 7 500 501 Totals: 502 Hits: 26098 503 Entries: 64 504 Dropped: 0 505 506 We can also add multiple fields to the 'values' parameter. For 507 example, we might want to see the total number of bytes allocated 508 alongside bytes requested, and display the result sorted by bytes 509 allocated in a descending order:: 510 511 # echo 'hist:keys=call_site.sym:values=bytes_req,bytes_alloc:sort=bytes_alloc.descending' > \ 512 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 513 514 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist 515 # trigger info: hist:keys=call_site.sym:vals=bytes_req,bytes_alloc:sort=bytes_alloc.descending:size=2048 [active] 516 517 { call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 7403 bytes_req: 4084360 bytes_alloc: 5958016 518 { call_site: [ffffffff811e2a1b] seq_buf_alloc } hitcount: 541 bytes_req: 2213968 bytes_alloc: 2228224 519 { call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 7404 bytes_req: 1066176 bytes_alloc: 1421568 520 { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 1565 bytes_req: 557368 bytes_alloc: 1037760 521 { call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 9557 bytes_req: 595778 bytes_alloc: 695744 522 { call_site: [ffffffffa045e646] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 5839 bytes_req: 430680 bytes_alloc: 470400 523 { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 2388 bytes_req: 324768 bytes_alloc: 458496 524 { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 3911 bytes_req: 219016 bytes_alloc: 250304 525 { call_site: [ffffffff815f8d7b] sk_prot_alloc } hitcount: 235 bytes_req: 236880 bytes_alloc: 240640 526 { call_site: [ffffffff8137e559] sg_kmalloc } hitcount: 557 bytes_req: 169024 bytes_alloc: 221760 527 { call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 9378 bytes_req: 187548 bytes_alloc: 206312 528 { call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 1519 bytes_req: 157976 bytes_alloc: 194432 529 . 530 . 531 . 532 { call_site: [ffffffff8109bd3b] sched_autogroup_create_attach } hitcount: 2 bytes_req: 144 bytes_alloc: 192 533 { call_site: [ffffffff81097ee8] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128 534 { call_site: [ffffffff8109524a] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128 535 { call_site: [ffffffff81095225] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128 536 { call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128 537 { call_site: [ffffffff81213e80] load_elf_binary } hitcount: 3 bytes_req: 84 bytes_alloc: 96 538 { call_site: [ffffffff81079a2e] kthread_create_on_node } hitcount: 1 bytes_req: 56 bytes_alloc: 64 539 { call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7 bytes_alloc: 8 540 { call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8 bytes_alloc: 8 541 { call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7 bytes_alloc: 8 542 543 Totals: 544 Hits: 66598 545 Entries: 65 546 Dropped: 0 547 548 Finally, to finish off our kmalloc example, instead of simply having 549 the hist trigger display symbolic call_sites, we can have the hist 550 trigger additionally display the complete set of kernel stack traces 551 that led to each call_site. To do that, we simply use the special 552 value 'stacktrace' for the key parameter:: 553 554 # echo 'hist:keys=stacktrace:values=bytes_req,bytes_alloc:sort=bytes_alloc' > \ 555 /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger 556 557 The above trigger will use the kernel stack trace in effect when an 558 event is triggered as the key for the hash table. This allows the 559 enumeration of every kernel callpath that led up to a particular 560 event, along with a running total of any of the event fields for 561 that event. Here we tally bytes requested and bytes allocated for 562 every callpath in the system that led up to a kmalloc (in this case 563 every callpath to a kmalloc for a kernel compile):: 564 565 # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist 566 # trigger info: hist:keys=stacktrace:vals=bytes_req,bytes_alloc:sort=bytes_alloc:size=2048 [active] 567 568 { stacktrace: 569 __kmalloc_track_caller+0x10b/0x1a0 570 kmemdup+0x20/0x50 571 hidraw_report_event+0x8a/0x120 [hid] 572 hid_report_raw_event+0x3ea/0x440 [hid] 573 hid_input_report+0x112/0x190 [hid] 574 hid_irq_in+0xc2/0x260 [usbhid] 575 __usb_hcd_giveback_urb+0x72/0x120 576 usb_giveback_urb_bh+0x9e/0xe0 577 tasklet_hi_action+0xf8/0x100 578 __do_softirq+0x114/0x2c0 579 irq_exit+0xa5/0xb0 580 do_IRQ+0x5a/0xf0 581 ret_from_intr+0x0/0x30 582 cpuidle_enter+0x17/0x20 583 cpu_startup_entry+0x315/0x3e0 584 rest_init+0x7c/0x80 585 } hitcount: 3 bytes_req: 21 bytes_alloc: 24 586 { stacktrace: 587 __kmalloc_track_caller+0x10b/0x1a0 588 kmemdup+0x20/0x50 589 hidraw_report_event+0x8a/0x120 [hid] 590 hid_report_raw_event+0x3ea/0x440 [hid] 591 hid_input_report+0x112/0x190 [hid] 592 hid_irq_in+0xc2/0x260 [usbhid] 593 __usb_hcd_giveback_urb+0x72/0x120 594 usb_giveback_urb_bh+0x9e/0xe0 595 tasklet_hi_action+0xf8/0x100 596 __do_softirq+0x114/0x2c0 597 irq_exit+0xa5/0xb0 598 do_IRQ+0x5a/0xf0 599 ret_from_intr+0x0/0x30 600 } hitcount: 3 bytes_req: 21 bytes_alloc: 24 601 { stacktrace: 602 kmem_cache_alloc_trace+0xeb/0x150 603 aa_alloc_task_context+0x27/0x40 604 apparmor_cred_prepare+0x1f/0x50 605 security_prepare_creds+0x16/0x20 606 prepare_creds+0xdf/0x1a0 607 SyS_capset+0xb5/0x200 608 system_call_fastpath+0x12/0x6a 609 } hitcount: 1 bytes_req: 32 bytes_alloc: 32 610 . 611 . 612 . 613 { stacktrace: 614 __kmalloc+0x11b/0x1b0 615 i915_gem_execbuffer2+0x6c/0x2c0 [i915] 616 drm_ioctl+0x349/0x670 [drm] 617 do_vfs_ioctl+0x2f0/0x4f0 618 SyS_ioctl+0x81/0xa0 619 system_call_fastpath+0x12/0x6a 620 } hitcount: 17726 bytes_req: 13944120 bytes_alloc: 19593808 621 { stacktrace: 622 __kmalloc+0x11b/0x1b0 623 load_elf_phdrs+0x76/0xa0 624 load_elf_binary+0x102/0x1650 625 search_binary_handler+0x97/0x1d0 626 do_execveat_common.isra.34+0x551/0x6e0 627 SyS_execve+0x3a/0x50 628 return_from_execve+0x0/0x23 629 } hitcount: 33348 bytes_req: 17152128 bytes_alloc: 20226048 630 { stacktrace: 631 kmem_cache_alloc_trace+0xeb/0x150 632 apparmor_file_alloc_security+0x27/0x40 633 security_file_alloc+0x16/0x20 634 get_empty_filp+0x93/0x1c0 635 path_openat+0x31/0x5f0 636 do_filp_open+0x3a/0x90 637 do_sys_open+0x128/0x220 638 SyS_open+0x1e/0x20 639 system_call_fastpath+0x12/0x6a 640 } hitcount: 4766422 bytes_req: 9532844 bytes_alloc: 38131376 641 { stacktrace: 642 __kmalloc+0x11b/0x1b0 643 seq_buf_alloc+0x1b/0x50 644 seq_read+0x2cc/0x370 645 proc_reg_read+0x3d/0x80 646 __vfs_read+0x28/0xe0 647 vfs_read+0x86/0x140 648 SyS_read+0x46/0xb0 649 system_call_fastpath+0x12/0x6a 650 } hitcount: 19133 bytes_req: 78368768 bytes_alloc: 78368768 651 652 Totals: 653 Hits: 6085872 654 Entries: 253 655 Dropped: 0 656 657 If you key a hist trigger on common_pid, in order for example to 658 gather and display sorted totals for each process, you can use the 659 special .execname modifier to display the executable names for the 660 processes in the table rather than raw pids. The example below 661 keeps a per-process sum of total bytes read:: 662 663 # echo 'hist:key=common_pid.execname:val=count:sort=count.descending' > \ 664 /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger 665 666 # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/hist 667 # trigger info: hist:keys=common_pid.execname:vals=count:sort=count.descending:size=2048 [active] 668 669 { common_pid: gnome-terminal [ 3196] } hitcount: 280 count: 1093512 670 { common_pid: Xorg [ 1309] } hitcount: 525 count: 256640 671 { common_pid: compiz [ 2889] } hitcount: 59 count: 254400 672 { common_pid: bash [ 8710] } hitcount: 3 count: 66369 673 { common_pid: dbus-daemon-lau [ 8703] } hitcount: 49 count: 47739 674 { common_pid: irqbalance [ 1252] } hitcount: 27 count: 27648 675 { common_pid: 01ifupdown [ 8705] } hitcount: 3 count: 17216 676 { common_pid: dbus-daemon [ 772] } hitcount: 10 count: 12396 677 { common_pid: Socket Thread [ 8342] } hitcount: 11 count: 11264 678 { common_pid: nm-dhcp-client. [ 8701] } hitcount: 6 count: 7424 679 { common_pid: gmain [ 1315] } hitcount: 18 count: 6336 680 . 681 . 682 . 683 { common_pid: postgres [ 1892] } hitcount: 2 count: 32 684 { common_pid: postgres [ 1891] } hitcount: 2 count: 32 685 { common_pid: gmain [ 8704] } hitcount: 2 count: 32 686 { common_pid: upstart-dbus-br [ 2740] } hitcount: 21 count: 21 687 { common_pid: nm-dispatcher.a [ 8696] } hitcount: 1 count: 16 688 { common_pid: indicator-datet [ 2904] } hitcount: 1 count: 16 689 { common_pid: gdbus [ 2998] } hitcount: 1 count: 16 690 { common_pid: rtkit-daemon [ 2052] } hitcount: 1 count: 8 691 { common_pid: init [ 1] } hitcount: 2 count: 2 692 693 Totals: 694 Hits: 2116 695 Entries: 51 696 Dropped: 0 697 698 Similarly, if you key a hist trigger on syscall id, for example to 699 gather and display a list of systemwide syscall hits, you can use 700 the special .syscall modifier to display the syscall names rather 701 than raw ids. The example below keeps a running total of syscall 702 counts for the system during the run:: 703 704 # echo 'hist:key=id.syscall:val=hitcount' > \ 705 /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger 706 707 # cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist 708 # trigger info: hist:keys=id.syscall:vals=hitcount:sort=hitcount:size=2048 [active] 709 710 { id: sys_fsync [ 74] } hitcount: 1 711 { id: sys_newuname [ 63] } hitcount: 1 712 { id: sys_prctl [157] } hitcount: 1 713 { id: sys_statfs [137] } hitcount: 1 714 { id: sys_symlink [ 88] } hitcount: 1 715 { id: sys_sendmmsg [307] } hitcount: 1 716 { id: sys_semctl [ 66] } hitcount: 1 717 { id: sys_readlink [ 89] } hitcount: 3 718 { id: sys_bind [ 49] } hitcount: 3 719 { id: sys_getsockname [ 51] } hitcount: 3 720 { id: sys_unlink [ 87] } hitcount: 3 721 { id: sys_rename [ 82] } hitcount: 4 722 { id: unknown_syscall [ 58] } hitcount: 4 723 { id: sys_connect [ 42] } hitcount: 4 724 { id: sys_getpid [ 39] } hitcount: 4 725 . 726 . 727 . 728 { id: sys_rt_sigprocmask [ 14] } hitcount: 952 729 { id: sys_futex [202] } hitcount: 1534 730 { id: sys_write [ 1] } hitcount: 2689 731 { id: sys_setitimer [ 38] } hitcount: 2797 732 { id: sys_read [ 0] } hitcount: 3202 733 { id: sys_select [ 23] } hitcount: 3773 734 { id: sys_writev [ 20] } hitcount: 4531 735 { id: sys_poll [ 7] } hitcount: 8314 736 { id: sys_recvmsg [ 47] } hitcount: 13738 737 { id: sys_ioctl [ 16] } hitcount: 21843 738 739 Totals: 740 Hits: 67612 741 Entries: 72 742 Dropped: 0 743 744 The syscall counts above provide a rough overall picture of system 745 call activity on the system; we can see for example that the most 746 popular system call on this system was the 'sys_ioctl' system call. 747 748 We can use 'compound' keys to refine that number and provide some 749 further insight as to which processes exactly contribute to the 750 overall ioctl count. 751 752 The command below keeps a hitcount for every unique combination of 753 system call id and pid - the end result is essentially a table 754 that keeps a per-pid sum of system call hits. The results are 755 sorted using the system call id as the primary key, and the 756 hitcount sum as the secondary key:: 757 758 # echo 'hist:key=id.syscall,common_pid.execname:val=hitcount:sort=id,hitcount' > \ 759 /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger 760 761 # cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist 762 # trigger info: hist:keys=id.syscall,common_pid.execname:vals=hitcount:sort=id.syscall,hitcount:size=2048 [active] 763 764 { id: sys_read [ 0], common_pid: rtkit-daemon [ 1877] } hitcount: 1 765 { id: sys_read [ 0], common_pid: gdbus [ 2976] } hitcount: 1 766 { id: sys_read [ 0], common_pid: console-kit-dae [ 3400] } hitcount: 1 767 { id: sys_read [ 0], common_pid: postgres [ 1865] } hitcount: 1 768 { id: sys_read [ 0], common_pid: deja-dup-monito [ 3543] } hitcount: 2 769 { id: sys_read [ 0], common_pid: NetworkManager [ 890] } hitcount: 2 770 { id: sys_read [ 0], common_pid: evolution-calen [ 3048] } hitcount: 2 771 { id: sys_read [ 0], common_pid: postgres [ 1864] } hitcount: 2 772 { id: sys_read [ 0], common_pid: nm-applet [ 3022] } hitcount: 2 773 { id: sys_read [ 0], common_pid: whoopsie [ 1212] } hitcount: 2 774 . 775 . 776 . 777 { id: sys_ioctl [ 16], common_pid: bash [ 8479] } hitcount: 1 778 { id: sys_ioctl [ 16], common_pid: bash [ 3472] } hitcount: 12 779 { id: sys_ioctl [ 16], common_pid: gnome-terminal [ 3199] } hitcount: 16 780 { id: sys_ioctl [ 16], common_pid: Xorg [ 1267] } hitcount: 1808 781 { id: sys_ioctl [ 16], common_pid: compiz [ 2994] } hitcount: 5580 782 . 783 . 784 . 785 { id: sys_waitid [247], common_pid: upstart-dbus-br [ 2690] } hitcount: 3 786 { id: sys_waitid [247], common_pid: upstart-dbus-br [ 2688] } hitcount: 16 787 { id: sys_inotify_add_watch [254], common_pid: gmain [ 975] } hitcount: 2 788 { id: sys_inotify_add_watch [254], common_pid: gmain [ 3204] } hitcount: 4 789 { id: sys_inotify_add_watch [254], common_pid: gmain [ 2888] } hitcount: 4 790 { id: sys_inotify_add_watch [254], common_pid: gmain [ 3003] } hitcount: 4 791 { id: sys_inotify_add_watch [254], common_pid: gmain [ 2873] } hitcount: 4 792 { id: sys_inotify_add_watch [254], common_pid: gmain [ 3196] } hitcount: 6 793 { id: sys_openat [257], common_pid: java [ 2623] } hitcount: 2 794 { id: sys_eventfd2 [290], common_pid: ibus-ui-gtk3 [ 2760] } hitcount: 4 795 { id: sys_eventfd2 [290], common_pid: compiz [ 2994] } hitcount: 6 796 797 Totals: 798 Hits: 31536 799 Entries: 323 800 Dropped: 0 801 802 The above list does give us a breakdown of the ioctl syscall by 803 pid, but it also gives us quite a bit more than that, which we 804 don't really care about at the moment. Since we know the syscall 805 id for sys_ioctl (16, displayed next to the sys_ioctl name), we 806 can use that to filter out all the other syscalls:: 807 808 # echo 'hist:key=id.syscall,common_pid.execname:val=hitcount:sort=id,hitcount if id == 16' > \ 809 /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger 810 811 # cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist 812 # trigger info: hist:keys=id.syscall,common_pid.execname:vals=hitcount:sort=id.syscall,hitcount:size=2048 if id == 16 [active] 813 814 { id: sys_ioctl [ 16], common_pid: gmain [ 2769] } hitcount: 1 815 { id: sys_ioctl [ 16], common_pid: evolution-addre [ 8571] } hitcount: 1 816 { id: sys_ioctl [ 16], common_pid: gmain [ 3003] } hitcount: 1 817 { id: sys_ioctl [ 16], common_pid: gmain [ 2781] } hitcount: 1 818 { id: sys_ioctl [ 16], common_pid: gmain [ 2829] } hitcount: 1 819 { id: sys_ioctl [ 16], common_pid: bash [ 8726] } hitcount: 1 820 { id: sys_ioctl [ 16], common_pid: bash [ 8508] } hitcount: 1 821 { id: sys_ioctl [ 16], common_pid: gmain [ 2970] } hitcount: 1 822 { id: sys_ioctl [ 16], common_pid: gmain [ 2768] } hitcount: 1 823 . 824 . 825 . 826 { id: sys_ioctl [ 16], common_pid: pool [ 8559] } hitcount: 45 827 { id: sys_ioctl [ 16], common_pid: pool [ 8555] } hitcount: 48 828 { id: sys_ioctl [ 16], common_pid: pool [ 8551] } hitcount: 48 829 { id: sys_ioctl [ 16], common_pid: avahi-daemon [ 896] } hitcount: 66 830 { id: sys_ioctl [ 16], common_pid: Xorg [ 1267] } hitcount: 26674 831 { id: sys_ioctl [ 16], common_pid: compiz [ 2994] } hitcount: 73443 832 833 Totals: 834 Hits: 101162 835 Entries: 103 836 Dropped: 0 837 838 The above output shows that 'compiz' and 'Xorg' are far and away 839 the heaviest ioctl callers (which might lead to questions about 840 whether they really need to be making all those calls and to 841 possible avenues for further investigation.) 842 843 The compound key examples used a key and a sum value (hitcount) to 844 sort the output, but we can just as easily use two keys instead. 845 Here's an example where we use a compound key composed of the the 846 common_pid and size event fields. Sorting with pid as the primary 847 key and 'size' as the secondary key allows us to display an 848 ordered summary of the recvfrom sizes, with counts, received by 849 each process:: 850 851 # echo 'hist:key=common_pid.execname,size:val=hitcount:sort=common_pid,size' > \ 852 /sys/kernel/debug/tracing/events/syscalls/sys_enter_recvfrom/trigger 853 854 # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_recvfrom/hist 855 # trigger info: hist:keys=common_pid.execname,size:vals=hitcount:sort=common_pid.execname,size:size=2048 [active] 856 857 { common_pid: smbd [ 784], size: 4 } hitcount: 1 858 { common_pid: dnsmasq [ 1412], size: 4096 } hitcount: 672 859 { common_pid: postgres [ 1796], size: 1000 } hitcount: 6 860 { common_pid: postgres [ 1867], size: 1000 } hitcount: 10 861 { common_pid: bamfdaemon [ 2787], size: 28 } hitcount: 2 862 { common_pid: bamfdaemon [ 2787], size: 14360 } hitcount: 1 863 { common_pid: compiz [ 2994], size: 8 } hitcount: 1 864 { common_pid: compiz [ 2994], size: 20 } hitcount: 11 865 { common_pid: gnome-terminal [ 3199], size: 4 } hitcount: 2 866 { common_pid: firefox [ 8817], size: 4 } hitcount: 1 867 { common_pid: firefox [ 8817], size: 8 } hitcount: 5 868 { common_pid: firefox [ 8817], size: 588 } hitcount: 2 869 { common_pid: firefox [ 8817], size: 628 } hitcount: 1 870 { common_pid: firefox [ 8817], size: 6944 } hitcount: 1 871 { common_pid: firefox [ 8817], size: 408880 } hitcount: 2 872 { common_pid: firefox [ 8822], size: 8 } hitcount: 2 873 { common_pid: firefox [ 8822], size: 160 } hitcount: 2 874 { common_pid: firefox [ 8822], size: 320 } hitcount: 2 875 { common_pid: firefox [ 8822], size: 352 } hitcount: 1 876 . 877 . 878 . 879 { common_pid: pool [ 8923], size: 1960 } hitcount: 10 880 { common_pid: pool [ 8923], size: 2048 } hitcount: 10 881 { common_pid: pool [ 8924], size: 1960 } hitcount: 10 882 { common_pid: pool [ 8924], size: 2048 } hitcount: 10 883 { common_pid: pool [ 8928], size: 1964 } hitcount: 4 884 { common_pid: pool [ 8928], size: 1965 } hitcount: 2 885 { common_pid: pool [ 8928], size: 2048 } hitcount: 6 886 { common_pid: pool [ 8929], size: 1982 } hitcount: 1 887 { common_pid: pool [ 8929], size: 2048 } hitcount: 1 888 889 Totals: 890 Hits: 2016 891 Entries: 224 892 Dropped: 0 893 894 The above example also illustrates the fact that although a compound 895 key is treated as a single entity for hashing purposes, the sub-keys 896 it's composed of can be accessed independently. 897 898 The next example uses a string field as the hash key and 899 demonstrates how you can manually pause and continue a hist trigger. 900 In this example, we'll aggregate fork counts and don't expect a 901 large number of entries in the hash table, so we'll drop it to a 902 much smaller number, say 256:: 903 904 # echo 'hist:key=child_comm:val=hitcount:size=256' > \ 905 /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger 906 907 # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist 908 # trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [active] 909 910 { child_comm: dconf worker } hitcount: 1 911 { child_comm: ibus-daemon } hitcount: 1 912 { child_comm: whoopsie } hitcount: 1 913 { child_comm: smbd } hitcount: 1 914 { child_comm: gdbus } hitcount: 1 915 { child_comm: kthreadd } hitcount: 1 916 { child_comm: dconf worker } hitcount: 1 917 { child_comm: evolution-alarm } hitcount: 2 918 { child_comm: Socket Thread } hitcount: 2 919 { child_comm: postgres } hitcount: 2 920 { child_comm: bash } hitcount: 3 921 { child_comm: compiz } hitcount: 3 922 { child_comm: evolution-sourc } hitcount: 4 923 { child_comm: dhclient } hitcount: 4 924 { child_comm: pool } hitcount: 5 925 { child_comm: nm-dispatcher.a } hitcount: 8 926 { child_comm: firefox } hitcount: 8 927 { child_comm: dbus-daemon } hitcount: 8 928 { child_comm: glib-pacrunner } hitcount: 10 929 { child_comm: evolution } hitcount: 23 930 931 Totals: 932 Hits: 89 933 Entries: 20 934 Dropped: 0 935 936 If we want to pause the hist trigger, we can simply append :pause to 937 the command that started the trigger. Notice that the trigger info 938 displays as [paused]:: 939 940 # echo 'hist:key=child_comm:val=hitcount:size=256:pause' >> \ 941 /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger 942 943 # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist 944 # trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [paused] 945 946 { child_comm: dconf worker } hitcount: 1 947 { child_comm: kthreadd } hitcount: 1 948 { child_comm: dconf worker } hitcount: 1 949 { child_comm: gdbus } hitcount: 1 950 { child_comm: ibus-daemon } hitcount: 1 951 { child_comm: Socket Thread } hitcount: 2 952 { child_comm: evolution-alarm } hitcount: 2 953 { child_comm: smbd } hitcount: 2 954 { child_comm: bash } hitcount: 3 955 { child_comm: whoopsie } hitcount: 3 956 { child_comm: compiz } hitcount: 3 957 { child_comm: evolution-sourc } hitcount: 4 958 { child_comm: pool } hitcount: 5 959 { child_comm: postgres } hitcount: 6 960 { child_comm: firefox } hitcount: 8 961 { child_comm: dhclient } hitcount: 10 962 { child_comm: emacs } hitcount: 12 963 { child_comm: dbus-daemon } hitcount: 20 964 { child_comm: nm-dispatcher.a } hitcount: 20 965 { child_comm: evolution } hitcount: 35 966 { child_comm: glib-pacrunner } hitcount: 59 967 968 Totals: 969 Hits: 199 970 Entries: 21 971 Dropped: 0 972 973 To manually continue having the trigger aggregate events, append 974 :cont instead. Notice that the trigger info displays as [active] 975 again, and the data has changed:: 976 977 # echo 'hist:key=child_comm:val=hitcount:size=256:cont' >> \ 978 /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger 979 980 # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist 981 # trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [active] 982 983 { child_comm: dconf worker } hitcount: 1 984 { child_comm: dconf worker } hitcount: 1 985 { child_comm: kthreadd } hitcount: 1 986 { child_comm: gdbus } hitcount: 1 987 { child_comm: ibus-daemon } hitcount: 1 988 { child_comm: Socket Thread } hitcount: 2 989 { child_comm: evolution-alarm } hitcount: 2 990 { child_comm: smbd } hitcount: 2 991 { child_comm: whoopsie } hitcount: 3 992 { child_comm: compiz } hitcount: 3 993 { child_comm: evolution-sourc } hitcount: 4 994 { child_comm: bash } hitcount: 5 995 { child_comm: pool } hitcount: 5 996 { child_comm: postgres } hitcount: 6 997 { child_comm: firefox } hitcount: 8 998 { child_comm: dhclient } hitcount: 11 999 { child_comm: emacs } hitcount: 12 1000 { child_comm: dbus-daemon } hitcount: 22 1001 { child_comm: nm-dispatcher.a } hitcount: 22 1002 { child_comm: evolution } hitcount: 35 1003 { child_comm: glib-pacrunner } hitcount: 59 1004 1005 Totals: 1006 Hits: 206 1007 Entries: 21 1008 Dropped: 0 1009 1010 The previous example showed how to start and stop a hist trigger by 1011 appending 'pause' and 'continue' to the hist trigger command. A 1012 hist trigger can also be started in a paused state by initially 1013 starting the trigger with ':pause' appended. This allows you to 1014 start the trigger only when you're ready to start collecting data 1015 and not before. For example, you could start the trigger in a 1016 paused state, then unpause it and do something you want to measure, 1017 then pause the trigger again when done. 1018 1019 Of course, doing this manually can be difficult and error-prone, but 1020 it is possible to automatically start and stop a hist trigger based 1021 on some condition, via the enable_hist and disable_hist triggers. 1022 1023 For example, suppose we wanted to take a look at the relative 1024 weights in terms of skb length for each callpath that leads to a 1025 netif_receieve_skb event when downloading a decent-sized file using 1026 wget. 1027 1028 First we set up an initially paused stacktrace trigger on the 1029 netif_receive_skb event:: 1030 1031 # echo 'hist:key=stacktrace:vals=len:pause' > \ 1032 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1033 1034 Next, we set up an 'enable_hist' trigger on the sched_process_exec 1035 event, with an 'if filename==/usr/bin/wget' filter. The effect of 1036 this new trigger is that it will 'unpause' the hist trigger we just 1037 set up on netif_receive_skb if and only if it sees a 1038 sched_process_exec event with a filename of '/usr/bin/wget'. When 1039 that happens, all netif_receive_skb events are aggregated into a 1040 hash table keyed on stacktrace:: 1041 1042 # echo 'enable_hist:net:netif_receive_skb if filename==/usr/bin/wget' > \ 1043 /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger 1044 1045 The aggregation continues until the netif_receive_skb is paused 1046 again, which is what the following disable_hist event does by 1047 creating a similar setup on the sched_process_exit event, using the 1048 filter 'comm==wget':: 1049 1050 # echo 'disable_hist:net:netif_receive_skb if comm==wget' > \ 1051 /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger 1052 1053 Whenever a process exits and the comm field of the disable_hist 1054 trigger filter matches 'comm==wget', the netif_receive_skb hist 1055 trigger is disabled. 1056 1057 The overall effect is that netif_receive_skb events are aggregated 1058 into the hash table for only the duration of the wget. Executing a 1059 wget command and then listing the 'hist' file will display the 1060 output generated by the wget command:: 1061 1062 $ wget https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.19.xz 1063 1064 # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist 1065 # trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused] 1066 1067 { stacktrace: 1068 __netif_receive_skb_core+0x46d/0x990 1069 __netif_receive_skb+0x18/0x60 1070 netif_receive_skb_internal+0x23/0x90 1071 napi_gro_receive+0xc8/0x100 1072 ieee80211_deliver_skb+0xd6/0x270 [mac80211] 1073 ieee80211_rx_handlers+0xccf/0x22f0 [mac80211] 1074 ieee80211_prepare_and_rx_handle+0x4e7/0xc40 [mac80211] 1075 ieee80211_rx+0x31d/0x900 [mac80211] 1076 iwlagn_rx_reply_rx+0x3db/0x6f0 [iwldvm] 1077 iwl_rx_dispatch+0x8e/0xf0 [iwldvm] 1078 iwl_pcie_irq_handler+0xe3c/0x12f0 [iwlwifi] 1079 irq_thread_fn+0x20/0x50 1080 irq_thread+0x11f/0x150 1081 kthread+0xd2/0xf0 1082 ret_from_fork+0x42/0x70 1083 } hitcount: 85 len: 28884 1084 { stacktrace: 1085 __netif_receive_skb_core+0x46d/0x990 1086 __netif_receive_skb+0x18/0x60 1087 netif_receive_skb_internal+0x23/0x90 1088 napi_gro_complete+0xa4/0xe0 1089 dev_gro_receive+0x23a/0x360 1090 napi_gro_receive+0x30/0x100 1091 ieee80211_deliver_skb+0xd6/0x270 [mac80211] 1092 ieee80211_rx_handlers+0xccf/0x22f0 [mac80211] 1093 ieee80211_prepare_and_rx_handle+0x4e7/0xc40 [mac80211] 1094 ieee80211_rx+0x31d/0x900 [mac80211] 1095 iwlagn_rx_reply_rx+0x3db/0x6f0 [iwldvm] 1096 iwl_rx_dispatch+0x8e/0xf0 [iwldvm] 1097 iwl_pcie_irq_handler+0xe3c/0x12f0 [iwlwifi] 1098 irq_thread_fn+0x20/0x50 1099 irq_thread+0x11f/0x150 1100 kthread+0xd2/0xf0 1101 } hitcount: 98 len: 664329 1102 { stacktrace: 1103 __netif_receive_skb_core+0x46d/0x990 1104 __netif_receive_skb+0x18/0x60 1105 process_backlog+0xa8/0x150 1106 net_rx_action+0x15d/0x340 1107 __do_softirq+0x114/0x2c0 1108 do_softirq_own_stack+0x1c/0x30 1109 do_softirq+0x65/0x70 1110 __local_bh_enable_ip+0xb5/0xc0 1111 ip_finish_output+0x1f4/0x840 1112 ip_output+0x6b/0xc0 1113 ip_local_out_sk+0x31/0x40 1114 ip_send_skb+0x1a/0x50 1115 udp_send_skb+0x173/0x2a0 1116 udp_sendmsg+0x2bf/0x9f0 1117 inet_sendmsg+0x64/0xa0 1118 sock_sendmsg+0x3d/0x50 1119 } hitcount: 115 len: 13030 1120 { stacktrace: 1121 __netif_receive_skb_core+0x46d/0x990 1122 __netif_receive_skb+0x18/0x60 1123 netif_receive_skb_internal+0x23/0x90 1124 napi_gro_complete+0xa4/0xe0 1125 napi_gro_flush+0x6d/0x90 1126 iwl_pcie_irq_handler+0x92a/0x12f0 [iwlwifi] 1127 irq_thread_fn+0x20/0x50 1128 irq_thread+0x11f/0x150 1129 kthread+0xd2/0xf0 1130 ret_from_fork+0x42/0x70 1131 } hitcount: 934 len: 5512212 1132 1133 Totals: 1134 Hits: 1232 1135 Entries: 4 1136 Dropped: 0 1137 1138 The above shows all the netif_receive_skb callpaths and their total 1139 lengths for the duration of the wget command. 1140 1141 The 'clear' hist trigger param can be used to clear the hash table. 1142 Suppose we wanted to try another run of the previous example but 1143 this time also wanted to see the complete list of events that went 1144 into the histogram. In order to avoid having to set everything up 1145 again, we can just clear the histogram first:: 1146 1147 # echo 'hist:key=stacktrace:vals=len:clear' >> \ 1148 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1149 1150 Just to verify that it is in fact cleared, here's what we now see in 1151 the hist file:: 1152 1153 # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist 1154 # trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused] 1155 1156 Totals: 1157 Hits: 0 1158 Entries: 0 1159 Dropped: 0 1160 1161 Since we want to see the detailed list of every netif_receive_skb 1162 event occurring during the new run, which are in fact the same 1163 events being aggregated into the hash table, we add some additional 1164 'enable_event' events to the triggering sched_process_exec and 1165 sched_process_exit events as such:: 1166 1167 # echo 'enable_event:net:netif_receive_skb if filename==/usr/bin/wget' > \ 1168 /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger 1169 1170 # echo 'disable_event:net:netif_receive_skb if comm==wget' > \ 1171 /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger 1172 1173 If you read the trigger files for the sched_process_exec and 1174 sched_process_exit triggers, you should see two triggers for each: 1175 one enabling/disabling the hist aggregation and the other 1176 enabling/disabling the logging of events:: 1177 1178 # cat /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger 1179 enable_event:net:netif_receive_skb:unlimited if filename==/usr/bin/wget 1180 enable_hist:net:netif_receive_skb:unlimited if filename==/usr/bin/wget 1181 1182 # cat /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger 1183 enable_event:net:netif_receive_skb:unlimited if comm==wget 1184 disable_hist:net:netif_receive_skb:unlimited if comm==wget 1185 1186 In other words, whenever either of the sched_process_exec or 1187 sched_process_exit events is hit and matches 'wget', it enables or 1188 disables both the histogram and the event log, and what you end up 1189 with is a hash table and set of events just covering the specified 1190 duration. Run the wget command again:: 1191 1192 $ wget https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.19.xz 1193 1194 Displaying the 'hist' file should show something similar to what you 1195 saw in the last run, but this time you should also see the 1196 individual events in the trace file:: 1197 1198 # cat /sys/kernel/debug/tracing/trace 1199 1200 # tracer: nop 1201 # 1202 # entries-in-buffer/entries-written: 183/1426 #P:4 1203 # 1204 # _-----=> irqs-off 1205 # / _----=> need-resched 1206 # | / _---=> hardirq/softirq 1207 # || / _--=> preempt-depth 1208 # ||| / delay 1209 # TASK-PID CPU# |||| TIMESTAMP FUNCTION 1210 # | | | |||| | | 1211 wget-15108 [000] ..s1 31769.606929: netif_receive_skb: dev=lo skbaddr=ffff88009c353100 len=60 1212 wget-15108 [000] ..s1 31769.606999: netif_receive_skb: dev=lo skbaddr=ffff88009c353200 len=60 1213 dnsmasq-1382 [000] ..s1 31769.677652: netif_receive_skb: dev=lo skbaddr=ffff88009c352b00 len=130 1214 dnsmasq-1382 [000] ..s1 31769.685917: netif_receive_skb: dev=lo skbaddr=ffff88009c352200 len=138 1215 ##### CPU 2 buffer started #### 1216 irq/29-iwlwifi-559 [002] ..s. 31772.031529: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433d00 len=2948 1217 irq/29-iwlwifi-559 [002] ..s. 31772.031572: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d432200 len=1500 1218 irq/29-iwlwifi-559 [002] ..s. 31772.032196: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433100 len=2948 1219 irq/29-iwlwifi-559 [002] ..s. 31772.032761: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433000 len=2948 1220 irq/29-iwlwifi-559 [002] ..s. 31772.033220: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d432e00 len=1500 1221 . 1222 . 1223 . 1224 1225 The following example demonstrates how multiple hist triggers can be 1226 attached to a given event. This capability can be useful for 1227 creating a set of different summaries derived from the same set of 1228 events, or for comparing the effects of different filters, among 1229 other things:: 1230 1231 # echo 'hist:keys=skbaddr.hex:vals=len if len < 0' >> \ 1232 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1233 # echo 'hist:keys=skbaddr.hex:vals=len if len > 4096' >> \ 1234 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1235 # echo 'hist:keys=skbaddr.hex:vals=len if len == 256' >> \ 1236 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1237 # echo 'hist:keys=skbaddr.hex:vals=len' >> \ 1238 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1239 # echo 'hist:keys=len:vals=common_preempt_count' >> \ 1240 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1241 1242 The above set of commands create four triggers differing only in 1243 their filters, along with a completely different though fairly 1244 nonsensical trigger. Note that in order to append multiple hist 1245 triggers to the same file, you should use the '>>' operator to 1246 append them ('>' will also add the new hist trigger, but will remove 1247 any existing hist triggers beforehand). 1248 1249 Displaying the contents of the 'hist' file for the event shows the 1250 contents of all five histograms:: 1251 1252 # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist 1253 1254 # event histogram 1255 # 1256 # trigger info: hist:keys=len:vals=hitcount,common_preempt_count:sort=hitcount:size=2048 [active] 1257 # 1258 1259 { len: 176 } hitcount: 1 common_preempt_count: 0 1260 { len: 223 } hitcount: 1 common_preempt_count: 0 1261 { len: 4854 } hitcount: 1 common_preempt_count: 0 1262 { len: 395 } hitcount: 1 common_preempt_count: 0 1263 { len: 177 } hitcount: 1 common_preempt_count: 0 1264 { len: 446 } hitcount: 1 common_preempt_count: 0 1265 { len: 1601 } hitcount: 1 common_preempt_count: 0 1266 . 1267 . 1268 . 1269 { len: 1280 } hitcount: 66 common_preempt_count: 0 1270 { len: 116 } hitcount: 81 common_preempt_count: 40 1271 { len: 708 } hitcount: 112 common_preempt_count: 0 1272 { len: 46 } hitcount: 221 common_preempt_count: 0 1273 { len: 1264 } hitcount: 458 common_preempt_count: 0 1274 1275 Totals: 1276 Hits: 1428 1277 Entries: 147 1278 Dropped: 0 1279 1280 1281 # event histogram 1282 # 1283 # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active] 1284 # 1285 1286 { skbaddr: ffff8800baee5e00 } hitcount: 1 len: 130 1287 { skbaddr: ffff88005f3d5600 } hitcount: 1 len: 1280 1288 { skbaddr: ffff88005f3d4900 } hitcount: 1 len: 1280 1289 { skbaddr: ffff88009fed6300 } hitcount: 1 len: 115 1290 { skbaddr: ffff88009fe0ad00 } hitcount: 1 len: 115 1291 { skbaddr: ffff88008cdb1900 } hitcount: 1 len: 46 1292 { skbaddr: ffff880064b5ef00 } hitcount: 1 len: 118 1293 { skbaddr: ffff880044e3c700 } hitcount: 1 len: 60 1294 { skbaddr: ffff880100065900 } hitcount: 1 len: 46 1295 { skbaddr: ffff8800d46bd500 } hitcount: 1 len: 116 1296 { skbaddr: ffff88005f3d5f00 } hitcount: 1 len: 1280 1297 { skbaddr: ffff880100064700 } hitcount: 1 len: 365 1298 { skbaddr: ffff8800badb6f00 } hitcount: 1 len: 60 1299 . 1300 . 1301 . 1302 { skbaddr: ffff88009fe0be00 } hitcount: 27 len: 24677 1303 { skbaddr: ffff88009fe0a400 } hitcount: 27 len: 23052 1304 { skbaddr: ffff88009fe0b700 } hitcount: 31 len: 25589 1305 { skbaddr: ffff88009fe0b600 } hitcount: 32 len: 27326 1306 { skbaddr: ffff88006a462800 } hitcount: 68 len: 71678 1307 { skbaddr: ffff88006a463700 } hitcount: 70 len: 72678 1308 { skbaddr: ffff88006a462b00 } hitcount: 71 len: 77589 1309 { skbaddr: ffff88006a463600 } hitcount: 73 len: 71307 1310 { skbaddr: ffff88006a462200 } hitcount: 81 len: 81032 1311 1312 Totals: 1313 Hits: 1451 1314 Entries: 318 1315 Dropped: 0 1316 1317 1318 # event histogram 1319 # 1320 # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len == 256 [active] 1321 # 1322 1323 1324 Totals: 1325 Hits: 0 1326 Entries: 0 1327 Dropped: 0 1328 1329 1330 # event histogram 1331 # 1332 # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len > 4096 [active] 1333 # 1334 1335 { skbaddr: ffff88009fd2c300 } hitcount: 1 len: 7212 1336 { skbaddr: ffff8800d2bcce00 } hitcount: 1 len: 7212 1337 { skbaddr: ffff8800d2bcd700 } hitcount: 1 len: 7212 1338 { skbaddr: ffff8800d2bcda00 } hitcount: 1 len: 21492 1339 { skbaddr: ffff8800ae2e2d00 } hitcount: 1 len: 7212 1340 { skbaddr: ffff8800d2bcdb00 } hitcount: 1 len: 7212 1341 { skbaddr: ffff88006a4df500 } hitcount: 1 len: 4854 1342 { skbaddr: ffff88008ce47b00 } hitcount: 1 len: 18636 1343 { skbaddr: ffff8800ae2e2200 } hitcount: 1 len: 12924 1344 { skbaddr: ffff88005f3e1000 } hitcount: 1 len: 4356 1345 { skbaddr: ffff8800d2bcdc00 } hitcount: 2 len: 24420 1346 { skbaddr: ffff8800d2bcc200 } hitcount: 2 len: 12996 1347 1348 Totals: 1349 Hits: 14 1350 Entries: 12 1351 Dropped: 0 1352 1353 1354 # event histogram 1355 # 1356 # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len < 0 [active] 1357 # 1358 1359 1360 Totals: 1361 Hits: 0 1362 Entries: 0 1363 Dropped: 0 1364 1365 Named triggers can be used to have triggers share a common set of 1366 histogram data. This capability is mostly useful for combining the 1367 output of events generated by tracepoints contained inside inline 1368 functions, but names can be used in a hist trigger on any event. 1369 For example, these two triggers when hit will update the same 'len' 1370 field in the shared 'foo' histogram data:: 1371 1372 # echo 'hist:name=foo:keys=skbaddr.hex:vals=len' > \ 1373 /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger 1374 # echo 'hist:name=foo:keys=skbaddr.hex:vals=len' > \ 1375 /sys/kernel/debug/tracing/events/net/netif_rx/trigger 1376 1377 You can see that they're updating common histogram data by reading 1378 each event's hist files at the same time:: 1379 1380 # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist; 1381 cat /sys/kernel/debug/tracing/events/net/netif_rx/hist 1382 1383 # event histogram 1384 # 1385 # trigger info: hist:name=foo:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active] 1386 # 1387 1388 { skbaddr: ffff88000ad53500 } hitcount: 1 len: 46 1389 { skbaddr: ffff8800af5a1500 } hitcount: 1 len: 76 1390 { skbaddr: ffff8800d62a1900 } hitcount: 1 len: 46 1391 { skbaddr: ffff8800d2bccb00 } hitcount: 1 len: 468 1392 { skbaddr: ffff8800d3c69900 } hitcount: 1 len: 46 1393 { skbaddr: ffff88009ff09100 } hitcount: 1 len: 52 1394 { skbaddr: ffff88010f13ab00 } hitcount: 1 len: 168 1395 { skbaddr: ffff88006a54f400 } hitcount: 1 len: 46 1396 { skbaddr: ffff8800d2bcc500 } hitcount: 1 len: 260 1397 { skbaddr: ffff880064505000 } hitcount: 1 len: 46 1398 { skbaddr: ffff8800baf24e00 } hitcount: 1 len: 32 1399 { skbaddr: ffff88009fe0ad00 } hitcount: 1 len: 46 1400 { skbaddr: ffff8800d3edff00 } hitcount: 1 len: 44 1401 { skbaddr: ffff88009fe0b400 } hitcount: 1 len: 168 1402 { skbaddr: ffff8800a1c55a00 } hitcount: 1 len: 40 1403 { skbaddr: ffff8800d2bcd100 } hitcount: 1 len: 40 1404 { skbaddr: ffff880064505f00 } hitcount: 1 len: 174 1405 { skbaddr: ffff8800a8bff200 } hitcount: 1 len: 160 1406 { skbaddr: ffff880044e3cc00 } hitcount: 1 len: 76 1407 { skbaddr: ffff8800a8bfe700 } hitcount: 1 len: 46 1408 { skbaddr: ffff8800d2bcdc00 } hitcount: 1 len: 32 1409 { skbaddr: ffff8800a1f64800 } hitcount: 1 len: 46 1410 { skbaddr: ffff8800d2bcde00 } hitcount: 1 len: 988 1411 { skbaddr: ffff88006a5dea00 } hitcount: 1 len: 46 1412 { skbaddr: ffff88002e37a200 } hitcount: 1 len: 44 1413 { skbaddr: ffff8800a1f32c00 } hitcount: 2 len: 676 1414 { skbaddr: ffff88000ad52600 } hitcount: 2 len: 107 1415 { skbaddr: ffff8800a1f91e00 } hitcount: 2 len: 92 1416 { skbaddr: ffff8800af5a0200 } hitcount: 2 len: 142 1417 { skbaddr: ffff8800d2bcc600 } hitcount: 2 len: 220 1418 { skbaddr: ffff8800ba36f500 } hitcount: 2 len: 92 1419 { skbaddr: ffff8800d021f800 } hitcount: 2 len: 92 1420 { skbaddr: ffff8800a1f33600 } hitcount: 2 len: 675 1421 { skbaddr: ffff8800a8bfff00 } hitcount: 3 len: 138 1422 { skbaddr: ffff8800d62a1300 } hitcount: 3 len: 138 1423 { skbaddr: ffff88002e37a100 } hitcount: 4 len: 184 1424 { skbaddr: ffff880064504400 } hitcount: 4 len: 184 1425 { skbaddr: ffff8800a8bfec00 } hitcount: 4 len: 184 1426 { skbaddr: ffff88000ad53700 } hitcount: 5 len: 230 1427 { skbaddr: ffff8800d2bcdb00 } hitcount: 5 len: 196 1428 { skbaddr: ffff8800a1f90000 } hitcount: 6 len: 276 1429 { skbaddr: ffff88006a54f900 } hitcount: 6 len: 276 1430 1431 Totals: 1432 Hits: 81 1433 Entries: 42 1434 Dropped: 0 1435 # event histogram 1436 # 1437 # trigger info: hist:name=foo:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active] 1438 # 1439 1440 { skbaddr: ffff88000ad53500 } hitcount: 1 len: 46 1441 { skbaddr: ffff8800af5a1500 } hitcount: 1 len: 76 1442 { skbaddr: ffff8800d62a1900 } hitcount: 1 len: 46 1443 { skbaddr: ffff8800d2bccb00 } hitcount: 1 len: 468 1444 { skbaddr: ffff8800d3c69900 } hitcount: 1 len: 46 1445 { skbaddr: ffff88009ff09100 } hitcount: 1 len: 52 1446 { skbaddr: ffff88010f13ab00 } hitcount: 1 len: 168 1447 { skbaddr: ffff88006a54f400 } hitcount: 1 len: 46 1448 { skbaddr: ffff8800d2bcc500 } hitcount: 1 len: 260 1449 { skbaddr: ffff880064505000 } hitcount: 1 len: 46 1450 { skbaddr: ffff8800baf24e00 } hitcount: 1 len: 32 1451 { skbaddr: ffff88009fe0ad00 } hitcount: 1 len: 46 1452 { skbaddr: ffff8800d3edff00 } hitcount: 1 len: 44 1453 { skbaddr: ffff88009fe0b400 } hitcount: 1 len: 168 1454 { skbaddr: ffff8800a1c55a00 } hitcount: 1 len: 40 1455 { skbaddr: ffff8800d2bcd100 } hitcount: 1 len: 40 1456 { skbaddr: ffff880064505f00 } hitcount: 1 len: 174 1457 { skbaddr: ffff8800a8bff200 } hitcount: 1 len: 160 1458 { skbaddr: ffff880044e3cc00 } hitcount: 1 len: 76 1459 { skbaddr: ffff8800a8bfe700 } hitcount: 1 len: 46 1460 { skbaddr: ffff8800d2bcdc00 } hitcount: 1 len: 32 1461 { skbaddr: ffff8800a1f64800 } hitcount: 1 len: 46 1462 { skbaddr: ffff8800d2bcde00 } hitcount: 1 len: 988 1463 { skbaddr: ffff88006a5dea00 } hitcount: 1 len: 46 1464 { skbaddr: ffff88002e37a200 } hitcount: 1 len: 44 1465 { skbaddr: ffff8800a1f32c00 } hitcount: 2 len: 676 1466 { skbaddr: ffff88000ad52600 } hitcount: 2 len: 107 1467 { skbaddr: ffff8800a1f91e00 } hitcount: 2 len: 92 1468 { skbaddr: ffff8800af5a0200 } hitcount: 2 len: 142 1469 { skbaddr: ffff8800d2bcc600 } hitcount: 2 len: 220 1470 { skbaddr: ffff8800ba36f500 } hitcount: 2 len: 92 1471 { skbaddr: ffff8800d021f800 } hitcount: 2 len: 92 1472 { skbaddr: ffff8800a1f33600 } hitcount: 2 len: 675 1473 { skbaddr: ffff8800a8bfff00 } hitcount: 3 len: 138 1474 { skbaddr: ffff8800d62a1300 } hitcount: 3 len: 138 1475 { skbaddr: ffff88002e37a100 } hitcount: 4 len: 184 1476 { skbaddr: ffff880064504400 } hitcount: 4 len: 184 1477 { skbaddr: ffff8800a8bfec00 } hitcount: 4 len: 184 1478 { skbaddr: ffff88000ad53700 } hitcount: 5 len: 230 1479 { skbaddr: ffff8800d2bcdb00 } hitcount: 5 len: 196 1480 { skbaddr: ffff8800a1f90000 } hitcount: 6 len: 276 1481 { skbaddr: ffff88006a54f900 } hitcount: 6 len: 276 1482 1483 Totals: 1484 Hits: 81 1485 Entries: 42 1486 Dropped: 0 1487 1488 And here's an example that shows how to combine histogram data from 1489 any two events even if they don't share any 'compatible' fields 1490 other than 'hitcount' and 'stacktrace'. These commands create a 1491 couple of triggers named 'bar' using those fields:: 1492 1493 # echo 'hist:name=bar:key=stacktrace:val=hitcount' > \ 1494 /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger 1495 # echo 'hist:name=bar:key=stacktrace:val=hitcount' > \ 1496 /sys/kernel/debug/tracing/events/net/netif_rx/trigger 1497 1498 And displaying the output of either shows some interesting if 1499 somewhat confusing output:: 1500 1501 # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist 1502 # cat /sys/kernel/debug/tracing/events/net/netif_rx/hist 1503 1504 # event histogram 1505 # 1506 # trigger info: hist:name=bar:keys=stacktrace:vals=hitcount:sort=hitcount:size=2048 [active] 1507 # 1508 1509 { stacktrace: 1510 _do_fork+0x18e/0x330 1511 kernel_thread+0x29/0x30 1512 kthreadd+0x154/0x1b0 1513 ret_from_fork+0x3f/0x70 1514 } hitcount: 1 1515 { stacktrace: 1516 netif_rx_internal+0xb2/0xd0 1517 netif_rx_ni+0x20/0x70 1518 dev_loopback_xmit+0xaa/0xd0 1519 ip_mc_output+0x126/0x240 1520 ip_local_out_sk+0x31/0x40 1521 igmp_send_report+0x1e9/0x230 1522 igmp_timer_expire+0xe9/0x120 1523 call_timer_fn+0x39/0xf0 1524 run_timer_softirq+0x1e1/0x290 1525 __do_softirq+0xfd/0x290 1526 irq_exit+0x98/0xb0 1527 smp_apic_timer_interrupt+0x4a/0x60 1528 apic_timer_interrupt+0x6d/0x80 1529 cpuidle_enter+0x17/0x20 1530 call_cpuidle+0x3b/0x60 1531 cpu_startup_entry+0x22d/0x310 1532 } hitcount: 1 1533 { stacktrace: 1534 netif_rx_internal+0xb2/0xd0 1535 netif_rx_ni+0x20/0x70 1536 dev_loopback_xmit+0xaa/0xd0 1537 ip_mc_output+0x17f/0x240 1538 ip_local_out_sk+0x31/0x40 1539 ip_send_skb+0x1a/0x50 1540 udp_send_skb+0x13e/0x270 1541 udp_sendmsg+0x2bf/0x980 1542 inet_sendmsg+0x67/0xa0 1543 sock_sendmsg+0x38/0x50 1544 SYSC_sendto+0xef/0x170 1545 SyS_sendto+0xe/0x10 1546 entry_SYSCALL_64_fastpath+0x12/0x6a 1547 } hitcount: 2 1548 { stacktrace: 1549 netif_rx_internal+0xb2/0xd0 1550 netif_rx+0x1c/0x60 1551 loopback_xmit+0x6c/0xb0 1552 dev_hard_start_xmit+0x219/0x3a0 1553 __dev_queue_xmit+0x415/0x4f0 1554 dev_queue_xmit_sk+0x13/0x20 1555 ip_finish_output2+0x237/0x340 1556 ip_finish_output+0x113/0x1d0 1557 ip_output+0x66/0xc0 1558 ip_local_out_sk+0x31/0x40 1559 ip_send_skb+0x1a/0x50 1560 udp_send_skb+0x16d/0x270 1561 udp_sendmsg+0x2bf/0x980 1562 inet_sendmsg+0x67/0xa0 1563 sock_sendmsg+0x38/0x50 1564 ___sys_sendmsg+0x14e/0x270 1565 } hitcount: 76 1566 { stacktrace: 1567 netif_rx_internal+0xb2/0xd0 1568 netif_rx+0x1c/0x60 1569 loopback_xmit+0x6c/0xb0 1570 dev_hard_start_xmit+0x219/0x3a0 1571 __dev_queue_xmit+0x415/0x4f0 1572 dev_queue_xmit_sk+0x13/0x20 1573 ip_finish_output2+0x237/0x340 1574 ip_finish_output+0x113/0x1d0 1575 ip_output+0x66/0xc0 1576 ip_local_out_sk+0x31/0x40 1577 ip_send_skb+0x1a/0x50 1578 udp_send_skb+0x16d/0x270 1579 udp_sendmsg+0x2bf/0x980 1580 inet_sendmsg+0x67/0xa0 1581 sock_sendmsg+0x38/0x50 1582 ___sys_sendmsg+0x269/0x270 1583 } hitcount: 77 1584 { stacktrace: 1585 netif_rx_internal+0xb2/0xd0 1586 netif_rx+0x1c/0x60 1587 loopback_xmit+0x6c/0xb0 1588 dev_hard_start_xmit+0x219/0x3a0 1589 __dev_queue_xmit+0x415/0x4f0 1590 dev_queue_xmit_sk+0x13/0x20 1591 ip_finish_output2+0x237/0x340 1592 ip_finish_output+0x113/0x1d0 1593 ip_output+0x66/0xc0 1594 ip_local_out_sk+0x31/0x40 1595 ip_send_skb+0x1a/0x50 1596 udp_send_skb+0x16d/0x270 1597 udp_sendmsg+0x2bf/0x980 1598 inet_sendmsg+0x67/0xa0 1599 sock_sendmsg+0x38/0x50 1600 SYSC_sendto+0xef/0x170 1601 } hitcount: 88 1602 { stacktrace: 1603 _do_fork+0x18e/0x330 1604 SyS_clone+0x19/0x20 1605 entry_SYSCALL_64_fastpath+0x12/0x6a 1606 } hitcount: 244 1607 1608 Totals: 1609 Hits: 489 1610 Entries: 7 1611 Dropped: 0 1612 16132.2 Inter-event hist triggers 1614----------------------------- 1615 1616Inter-event hist triggers are hist triggers that combine values from 1617one or more other events and create a histogram using that data. Data 1618from an inter-event histogram can in turn become the source for 1619further combined histograms, thus providing a chain of related 1620histograms, which is important for some applications. 1621 1622The most important example of an inter-event quantity that can be used 1623in this manner is latency, which is simply a difference in timestamps 1624between two events. Although latency is the most important 1625inter-event quantity, note that because the support is completely 1626general across the trace event subsystem, any event field can be used 1627in an inter-event quantity. 1628 1629An example of a histogram that combines data from other histograms 1630into a useful chain would be a 'wakeupswitch latency' histogram that 1631combines a 'wakeup latency' histogram and a 'switch latency' 1632histogram. 1633 1634Normally, a hist trigger specification consists of a (possibly 1635compound) key along with one or more numeric values, which are 1636continually updated sums associated with that key. A histogram 1637specification in this case consists of individual key and value 1638specifications that refer to trace event fields associated with a 1639single event type. 1640 1641The inter-event hist trigger extension allows fields from multiple 1642events to be referenced and combined into a multi-event histogram 1643specification. In support of this overall goal, a few enabling 1644features have been added to the hist trigger support: 1645 1646 - In order to compute an inter-event quantity, a value from one 1647 event needs to saved and then referenced from another event. This 1648 requires the introduction of support for histogram 'variables'. 1649 1650 - The computation of inter-event quantities and their combination 1651 require some minimal amount of support for applying simple 1652 expressions to variables (+ and -). 1653 1654 - A histogram consisting of inter-event quantities isn't logically a 1655 histogram on either event (so having the 'hist' file for either 1656 event host the histogram output doesn't really make sense). To 1657 address the idea that the histogram is associated with a 1658 combination of events, support is added allowing the creation of 1659 'synthetic' events that are events derived from other events. 1660 These synthetic events are full-fledged events just like any other 1661 and can be used as such, as for instance to create the 1662 'combination' histograms mentioned previously. 1663 1664 - A set of 'actions' can be associated with histogram entries - 1665 these can be used to generate the previously mentioned synthetic 1666 events, but can also be used for other purposes, such as for 1667 example saving context when a 'max' latency has been hit. 1668 1669 - Trace events don't have a 'timestamp' associated with them, but 1670 there is an implicit timestamp saved along with an event in the 1671 underlying ftrace ring buffer. This timestamp is now exposed as a 1672 a synthetic field named 'common_timestamp' which can be used in 1673 histograms as if it were any other event field; it isn't an actual 1674 field in the trace format but rather is a synthesized value that 1675 nonetheless can be used as if it were an actual field. By default 1676 it is in units of nanoseconds; appending '.usecs' to a 1677 common_timestamp field changes the units to microseconds. 1678 1679A note on inter-event timestamps: If common_timestamp is used in a 1680histogram, the trace buffer is automatically switched over to using 1681absolute timestamps and the "global" trace clock, in order to avoid 1682bogus timestamp differences with other clocks that aren't coherent 1683across CPUs. This can be overridden by specifying one of the other 1684trace clocks instead, using the "clock=XXX" hist trigger attribute, 1685where XXX is any of the clocks listed in the tracing/trace_clock 1686pseudo-file. 1687 1688These features are described in more detail in the following sections. 1689 16902.2.1 Histogram Variables 1691------------------------- 1692 1693Variables are simply named locations used for saving and retrieving 1694values between matching events. A 'matching' event is defined as an 1695event that has a matching key - if a variable is saved for a histogram 1696entry corresponding to that key, any subsequent event with a matching 1697key can access that variable. 1698 1699A variable's value is normally available to any subsequent event until 1700it is set to something else by a subsequent event. The one exception 1701to that rule is that any variable used in an expression is essentially 1702'read-once' - once it's used by an expression in a subsequent event, 1703it's reset to its 'unset' state, which means it can't be used again 1704unless it's set again. This ensures not only that an event doesn't 1705use an uninitialized variable in a calculation, but that that variable 1706is used only once and not for any unrelated subsequent match. 1707 1708The basic syntax for saving a variable is to simply prefix a unique 1709variable name not corresponding to any keyword along with an '=' sign 1710to any event field. 1711 1712Either keys or values can be saved and retrieved in this way. This 1713creates a variable named 'ts0' for a histogram entry with the key 1714'next_pid':: 1715 1716 # echo 'hist:keys=next_pid:vals=$ts0:ts0=common_timestamp ... >> \ 1717 event/trigger 1718 1719The ts0 variable can be accessed by any subsequent event having the 1720same pid as 'next_pid'. 1721 1722Variable references are formed by prepending the variable name with 1723the '$' sign. Thus for example, the ts0 variable above would be 1724referenced as '$ts0' in expressions. 1725 1726Because 'vals=' is used, the common_timestamp variable value above 1727will also be summed as a normal histogram value would (though for a 1728timestamp it makes little sense). 1729 1730The below shows that a key value can also be saved in the same way:: 1731 1732 # echo 'hist:timer_pid=common_pid:key=timer_pid ...' >> event/trigger 1733 1734If a variable isn't a key variable or prefixed with 'vals=', the 1735associated event field will be saved in a variable but won't be summed 1736as a value:: 1737 1738 # echo 'hist:keys=next_pid:ts1=common_timestamp ...' >> event/trigger 1739 1740Multiple variables can be assigned at the same time. The below would 1741result in both ts0 and b being created as variables, with both 1742common_timestamp and field1 additionally being summed as values:: 1743 1744 # echo 'hist:keys=pid:vals=$ts0,$b:ts0=common_timestamp,b=field1 ...' >> \ 1745 event/trigger 1746 1747Note that variable assignments can appear either preceding or 1748following their use. The command below behaves identically to the 1749command above:: 1750 1751 # echo 'hist:keys=pid:ts0=common_timestamp,b=field1:vals=$ts0,$b ...' >> \ 1752 event/trigger 1753 1754Any number of variables not bound to a 'vals=' prefix can also be 1755assigned by simply separating them with colons. Below is the same 1756thing but without the values being summed in the histogram:: 1757 1758 # echo 'hist:keys=pid:ts0=common_timestamp:b=field1 ...' >> event/trigger 1759 1760Variables set as above can be referenced and used in expressions on 1761another event. 1762 1763For example, here's how a latency can be calculated:: 1764 1765 # echo 'hist:keys=pid,prio:ts0=common_timestamp ...' >> event1/trigger 1766 # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...' >> event2/trigger 1767 1768In the first line above, the event's timestamp is saved into the 1769variable ts0. In the next line, ts0 is subtracted from the second 1770event's timestamp to produce the latency, which is then assigned into 1771yet another variable, 'wakeup_lat'. The hist trigger below in turn 1772makes use of the wakeup_lat variable to compute a combined latency 1773using the same key and variable from yet another event:: 1774 1775 # echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ...' >> event3/trigger 1776 17772.2.2 Synthetic Events 1778---------------------- 1779 1780Synthetic events are user-defined events generated from hist trigger 1781variables or fields associated with one or more other events. Their 1782purpose is to provide a mechanism for displaying data spanning 1783multiple events consistent with the existing and already familiar 1784usage for normal events. 1785 1786To define a synthetic event, the user writes a simple specification 1787consisting of the name of the new event along with one or more 1788variables and their types, which can be any valid field type, 1789separated by semicolons, to the tracing/synthetic_events file. 1790 1791For instance, the following creates a new event named 'wakeup_latency' 1792with 3 fields: lat, pid, and prio. Each of those fields is simply a 1793variable reference to a variable on another event:: 1794 1795 # echo 'wakeup_latency \ 1796 u64 lat; \ 1797 pid_t pid; \ 1798 int prio' >> \ 1799 /sys/kernel/debug/tracing/synthetic_events 1800 1801Reading the tracing/synthetic_events file lists all the currently 1802defined synthetic events, in this case the event defined above:: 1803 1804 # cat /sys/kernel/debug/tracing/synthetic_events 1805 wakeup_latency u64 lat; pid_t pid; int prio 1806 1807An existing synthetic event definition can be removed by prepending 1808the command that defined it with a '!':: 1809 1810 # echo '!wakeup_latency u64 lat pid_t pid int prio' >> \ 1811 /sys/kernel/debug/tracing/synthetic_events 1812 1813At this point, there isn't yet an actual 'wakeup_latency' event 1814instantiated in the event subsystem - for this to happen, a 'hist 1815trigger action' needs to be instantiated and bound to actual fields 1816and variables defined on other events (see Section 2.2.3 below on 1817how that is done using hist trigger 'onmatch' action). Once that is 1818done, the 'wakeup_latency' synthetic event instance is created. 1819 1820A histogram can now be defined for the new synthetic event:: 1821 1822 # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \ 1823 /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger 1824 1825The new event is created under the tracing/events/synthetic/ directory 1826and looks and behaves just like any other event:: 1827 1828 # ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency 1829 enable filter format hist id trigger 1830 1831Like any other event, once a histogram is enabled for the event, the 1832output can be displayed by reading the event's 'hist' file. 1833 18342.2.3 Hist trigger 'handlers' and 'actions' 1835------------------------------------------- 1836 1837A hist trigger 'action' is a function that's executed (in most cases 1838conditionally) whenever a histogram entry is added or updated. 1839 1840When a histogram entry is added or updated, a hist trigger 'handler' 1841is what decides whether the corresponding action is actually invoked 1842or not. 1843 1844Hist trigger handlers and actions are paired together in the general 1845form: 1846 1847 <handler>.<action> 1848 1849To specify a handler.action pair for a given event, simply specify 1850that handler.action pair between colons in the hist trigger 1851specification. 1852 1853In theory, any handler can be combined with any action, but in 1854practice, not every handler.action combination is currently supported; 1855if a given handler.action combination isn't supported, the hist 1856trigger will fail with -EINVAL; 1857 1858The default 'handler.action' if none is explicity specified is as it 1859always has been, to simply update the set of values associated with an 1860entry. Some applications, however, may want to perform additional 1861actions at that point, such as generate another event, or compare and 1862save a maximum. 1863 1864The supported handlers and actions are listed below, and each is 1865described in more detail in the following paragraphs, in the context 1866of descriptions of some common and useful handler.action combinations. 1867 1868The available handlers are: 1869 1870 - onmatch(matching.event) - invoke action on any addition or update 1871 - onmax(var) - invoke action if var exceeds current max 1872 - onchange(var) - invoke action if var changes 1873 1874The available actions are: 1875 1876 - trace(<synthetic_event_name>,param list) - generate synthetic event 1877 - save(field,...) - save current event fields 1878 - snapshot() - snapshot the trace buffer 1879 1880The following commonly-used handler.action pairs are available: 1881 1882 - onmatch(matching.event).trace(<synthetic_event_name>,param list) 1883 1884 The 'onmatch(matching.event).trace(<synthetic_event_name>,param 1885 list)' hist trigger action is invoked whenever an event matches 1886 and the histogram entry would be added or updated. It causes the 1887 named synthetic event to be generated with the values given in the 1888 'param list'. The result is the generation of a synthetic event 1889 that consists of the values contained in those variables at the 1890 time the invoking event was hit. For example, if the synthetic 1891 event name is 'wakeup_latency', a wakeup_latency event is 1892 generated using onmatch(event).trace(wakeup_latency,arg1,arg2). 1893 1894 There is also an equivalent alternative form available for 1895 generating synthetic events. In this form, the synthetic event 1896 name is used as if it were a function name. For example, using 1897 the 'wakeup_latency' synthetic event name again, the 1898 wakeup_latency event would be generated by invoking it as if it 1899 were a function call, with the event field values passed in as 1900 arguments: onmatch(event).wakeup_latency(arg1,arg2). The syntax 1901 for this form is: 1902 1903 onmatch(matching.event).<synthetic_event_name>(param list) 1904 1905 In either case, the 'param list' consists of one or more 1906 parameters which may be either variables or fields defined on 1907 either the 'matching.event' or the target event. The variables or 1908 fields specified in the param list may be either fully-qualified 1909 or unqualified. If a variable is specified as unqualified, it 1910 must be unique between the two events. A field name used as a 1911 param can be unqualified if it refers to the target event, but 1912 must be fully qualified if it refers to the matching event. A 1913 fully-qualified name is of the form 'system.event_name.$var_name' 1914 or 'system.event_name.field'. 1915 1916 The 'matching.event' specification is simply the fully qualified 1917 event name of the event that matches the target event for the 1918 onmatch() functionality, in the form 'system.event_name'. 1919 1920 Finally, the number and type of variables/fields in the 'param 1921 list' must match the number and types of the fields in the 1922 synthetic event being generated. 1923 1924 As an example the below defines a simple synthetic event and uses 1925 a variable defined on the sched_wakeup_new event as a parameter 1926 when invoking the synthetic event. Here we define the synthetic 1927 event:: 1928 1929 # echo 'wakeup_new_test pid_t pid' >> \ 1930 /sys/kernel/debug/tracing/synthetic_events 1931 1932 # cat /sys/kernel/debug/tracing/synthetic_events 1933 wakeup_new_test pid_t pid 1934 1935 The following hist trigger both defines the missing testpid 1936 variable and specifies an onmatch() action that generates a 1937 wakeup_new_test synthetic event whenever a sched_wakeup_new event 1938 occurs, which because of the 'if comm == "cyclictest"' filter only 1939 happens when the executable is cyclictest:: 1940 1941 # echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\ 1942 wakeup_new_test($testpid) if comm=="cyclictest"' >> \ 1943 /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger 1944 1945 Or, equivalently, using the 'trace' keyword syntax: 1946 1947 # echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\ 1948 trace(wakeup_new_test,$testpid) if comm=="cyclictest"' >> \ 1949 /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger 1950 1951 Creating and displaying a histogram based on those events is now 1952 just a matter of using the fields and new synthetic event in the 1953 tracing/events/synthetic directory, as usual:: 1954 1955 # echo 'hist:keys=pid:sort=pid' >> \ 1956 /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger 1957 1958 Running 'cyclictest' should cause wakeup_new events to generate 1959 wakeup_new_test synthetic events which should result in histogram 1960 output in the wakeup_new_test event's hist file:: 1961 1962 # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/hist 1963 1964 A more typical usage would be to use two events to calculate a 1965 latency. The following example uses a set of hist triggers to 1966 produce a 'wakeup_latency' histogram. 1967 1968 First, we define a 'wakeup_latency' synthetic event:: 1969 1970 # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \ 1971 /sys/kernel/debug/tracing/synthetic_events 1972 1973 Next, we specify that whenever we see a sched_waking event for a 1974 cyclictest thread, save the timestamp in a 'ts0' variable:: 1975 1976 # echo 'hist:keys=$saved_pid:saved_pid=pid:ts0=common_timestamp.usecs \ 1977 if comm=="cyclictest"' >> \ 1978 /sys/kernel/debug/tracing/events/sched/sched_waking/trigger 1979 1980 Then, when the corresponding thread is actually scheduled onto the 1981 CPU by a sched_switch event, calculate the latency and use that 1982 along with another variable and an event field to generate a 1983 wakeup_latency synthetic event:: 1984 1985 # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:\ 1986 onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,\ 1987 $saved_pid,next_prio) if next_comm=="cyclictest"' >> \ 1988 /sys/kernel/debug/tracing/events/sched/sched_switch/trigger 1989 1990 We also need to create a histogram on the wakeup_latency synthetic 1991 event in order to aggregate the generated synthetic event data:: 1992 1993 # echo 'hist:keys=pid,prio,lat:sort=pid,lat' >> \ 1994 /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger 1995 1996 Finally, once we've run cyclictest to actually generate some 1997 events, we can see the output by looking at the wakeup_latency 1998 synthetic event's hist file:: 1999 2000 # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist 2001 2002 - onmax(var).save(field,.. .) 2003 2004 The 'onmax(var).save(field,...)' hist trigger action is invoked 2005 whenever the value of 'var' associated with a histogram entry 2006 exceeds the current maximum contained in that variable. 2007 2008 The end result is that the trace event fields specified as the 2009 onmax.save() params will be saved if 'var' exceeds the current 2010 maximum for that hist trigger entry. This allows context from the 2011 event that exhibited the new maximum to be saved for later 2012 reference. When the histogram is displayed, additional fields 2013 displaying the saved values will be printed. 2014 2015 As an example the below defines a couple of hist triggers, one for 2016 sched_waking and another for sched_switch, keyed on pid. Whenever 2017 a sched_waking occurs, the timestamp is saved in the entry 2018 corresponding to the current pid, and when the scheduler switches 2019 back to that pid, the timestamp difference is calculated. If the 2020 resulting latency, stored in wakeup_lat, exceeds the current 2021 maximum latency, the values specified in the save() fields are 2022 recorded:: 2023 2024 # echo 'hist:keys=pid:ts0=common_timestamp.usecs \ 2025 if comm=="cyclictest"' >> \ 2026 /sys/kernel/debug/tracing/events/sched/sched_waking/trigger 2027 2028 # echo 'hist:keys=next_pid:\ 2029 wakeup_lat=common_timestamp.usecs-$ts0:\ 2030 onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \ 2031 if next_comm=="cyclictest"' >> \ 2032 /sys/kernel/debug/tracing/events/sched/sched_switch/trigger 2033 2034 When the histogram is displayed, the max value and the saved 2035 values corresponding to the max are displayed following the rest 2036 of the fields:: 2037 2038 # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist 2039 { next_pid: 2255 } hitcount: 239 2040 common_timestamp-ts0: 0 2041 max: 27 2042 next_comm: cyclictest 2043 prev_pid: 0 prev_prio: 120 prev_comm: swapper/1 2044 2045 { next_pid: 2256 } hitcount: 2355 2046 common_timestamp-ts0: 0 2047 max: 49 next_comm: cyclictest 2048 prev_pid: 0 prev_prio: 120 prev_comm: swapper/0 2049 2050 Totals: 2051 Hits: 12970 2052 Entries: 2 2053 Dropped: 0 2054 2055 - onmax(var).snapshot() 2056 2057 The 'onmax(var).snapshot()' hist trigger action is invoked 2058 whenever the value of 'var' associated with a histogram entry 2059 exceeds the current maximum contained in that variable. 2060 2061 The end result is that a global snapshot of the trace buffer will 2062 be saved in the tracing/snapshot file if 'var' exceeds the current 2063 maximum for any hist trigger entry. 2064 2065 Note that in this case the maximum is a global maximum for the 2066 current trace instance, which is the maximum across all buckets of 2067 the histogram. The key of the specific trace event that caused 2068 the global maximum and the global maximum itself are displayed, 2069 along with a message stating that a snapshot has been taken and 2070 where to find it. The user can use the key information displayed 2071 to locate the corresponding bucket in the histogram for even more 2072 detail. 2073 2074 As an example the below defines a couple of hist triggers, one for 2075 sched_waking and another for sched_switch, keyed on pid. Whenever 2076 a sched_waking event occurs, the timestamp is saved in the entry 2077 corresponding to the current pid, and when the scheduler switches 2078 back to that pid, the timestamp difference is calculated. If the 2079 resulting latency, stored in wakeup_lat, exceeds the current 2080 maximum latency, a snapshot is taken. As part of the setup, all 2081 the scheduler events are also enabled, which are the events that 2082 will show up in the snapshot when it is taken at some point: 2083 2084 # echo 1 > /sys/kernel/debug/tracing/events/sched/enable 2085 2086 # echo 'hist:keys=pid:ts0=common_timestamp.usecs \ 2087 if comm=="cyclictest"' >> \ 2088 /sys/kernel/debug/tracing/events/sched/sched_waking/trigger 2089 2090 # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0: \ 2091 onmax($wakeup_lat).save(next_prio,next_comm,prev_pid,prev_prio, \ 2092 prev_comm):onmax($wakeup_lat).snapshot() \ 2093 if next_comm=="cyclictest"' >> \ 2094 /sys/kernel/debug/tracing/events/sched/sched_switch/trigger 2095 2096 When the histogram is displayed, for each bucket the max value 2097 and the saved values corresponding to the max are displayed 2098 following the rest of the fields. 2099 2100 If a snaphot was taken, there is also a message indicating that, 2101 along with the value and event that triggered the global maximum: 2102 2103 # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist 2104 { next_pid: 2101 } hitcount: 200 2105 max: 52 next_prio: 120 next_comm: cyclictest \ 2106 prev_pid: 0 prev_prio: 120 prev_comm: swapper/6 2107 2108 { next_pid: 2103 } hitcount: 1326 2109 max: 572 next_prio: 19 next_comm: cyclictest \ 2110 prev_pid: 0 prev_prio: 120 prev_comm: swapper/1 2111 2112 { next_pid: 2102 } hitcount: 1982 \ 2113 max: 74 next_prio: 19 next_comm: cyclictest \ 2114 prev_pid: 0 prev_prio: 120 prev_comm: swapper/5 2115 2116 Snapshot taken (see tracing/snapshot). Details: 2117 triggering value { onmax($wakeup_lat) }: 572 \ 2118 triggered by event with key: { next_pid: 2103 } 2119 2120 Totals: 2121 Hits: 3508 2122 Entries: 3 2123 Dropped: 0 2124 2125 In the above case, the event that triggered the global maximum has 2126 the key with next_pid == 2103. If you look at the bucket that has 2127 2103 as the key, you'll find the additional values save()'d along 2128 with the local maximum for that bucket, which should be the same 2129 as the global maximum (since that was the same value that 2130 triggered the global snapshot). 2131 2132 And finally, looking at the snapshot data should show at or near 2133 the end the event that triggered the snapshot (in this case you 2134 can verify the timestamps between the sched_waking and 2135 sched_switch events, which should match the time displayed in the 2136 global maximum): 2137 2138 # cat /sys/kernel/debug/tracing/snapshot 2139 2140 <...>-2103 [005] d..3 309.873125: sched_switch: prev_comm=cyclictest prev_pid=2103 prev_prio=19 prev_state=D ==> next_comm=swapper/5 next_pid=0 next_prio=120 2141 <idle>-0 [005] d.h3 309.873611: sched_waking: comm=cyclictest pid=2102 prio=19 target_cpu=005 2142 <idle>-0 [005] dNh4 309.873613: sched_wakeup: comm=cyclictest pid=2102 prio=19 target_cpu=005 2143 <idle>-0 [005] d..3 309.873616: sched_switch: prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=S ==> next_comm=cyclictest next_pid=2102 next_prio=19 2144 <...>-2102 [005] d..3 309.873625: sched_switch: prev_comm=cyclictest prev_pid=2102 prev_prio=19 prev_state=D ==> next_comm=swapper/5 next_pid=0 next_prio=120 2145 <idle>-0 [005] d.h3 309.874624: sched_waking: comm=cyclictest pid=2102 prio=19 target_cpu=005 2146 <idle>-0 [005] dNh4 309.874626: sched_wakeup: comm=cyclictest pid=2102 prio=19 target_cpu=005 2147 <idle>-0 [005] dNh3 309.874628: sched_waking: comm=cyclictest pid=2103 prio=19 target_cpu=005 2148 <idle>-0 [005] dNh4 309.874630: sched_wakeup: comm=cyclictest pid=2103 prio=19 target_cpu=005 2149 <idle>-0 [005] d..3 309.874633: sched_switch: prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=S ==> next_comm=cyclictest next_pid=2102 next_prio=19 2150 <idle>-0 [004] d.h3 309.874757: sched_waking: comm=gnome-terminal- pid=1699 prio=120 target_cpu=004 2151 <idle>-0 [004] dNh4 309.874762: sched_wakeup: comm=gnome-terminal- pid=1699 prio=120 target_cpu=004 2152 <idle>-0 [004] d..3 309.874766: sched_switch: prev_comm=swapper/4 prev_pid=0 prev_prio=120 prev_state=S ==> next_comm=gnome-terminal- next_pid=1699 next_prio=120 2153 gnome-terminal--1699 [004] d.h2 309.874941: sched_stat_runtime: comm=gnome-terminal- pid=1699 runtime=180706 [ns] vruntime=1126870572 [ns] 2154 <idle>-0 [003] d.s4 309.874956: sched_waking: comm=rcu_sched pid=9 prio=120 target_cpu=007 2155 <idle>-0 [003] d.s5 309.874960: sched_wake_idle_without_ipi: cpu=7 2156 <idle>-0 [003] d.s5 309.874961: sched_wakeup: comm=rcu_sched pid=9 prio=120 target_cpu=007 2157 <idle>-0 [007] d..3 309.874963: sched_switch: prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=S ==> next_comm=rcu_sched next_pid=9 next_prio=120 2158 rcu_sched-9 [007] d..3 309.874973: sched_stat_runtime: comm=rcu_sched pid=9 runtime=13646 [ns] vruntime=22531430286 [ns] 2159 rcu_sched-9 [007] d..3 309.874978: sched_switch: prev_comm=rcu_sched prev_pid=9 prev_prio=120 prev_state=R+ ==> next_comm=swapper/7 next_pid=0 next_prio=120 2160 <...>-2102 [005] d..4 309.874994: sched_migrate_task: comm=cyclictest pid=2103 prio=19 orig_cpu=5 dest_cpu=1 2161 <...>-2102 [005] d..4 309.875185: sched_wake_idle_without_ipi: cpu=1 2162 <idle>-0 [001] d..3 309.875200: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=S ==> next_comm=cyclictest next_pid=2103 next_prio=19 2163 2164 - onchange(var).save(field,.. .) 2165 2166 The 'onchange(var).save(field,...)' hist trigger action is invoked 2167 whenever the value of 'var' associated with a histogram entry 2168 changes. 2169 2170 The end result is that the trace event fields specified as the 2171 onchange.save() params will be saved if 'var' changes for that 2172 hist trigger entry. This allows context from the event that 2173 changed the value to be saved for later reference. When the 2174 histogram is displayed, additional fields displaying the saved 2175 values will be printed. 2176 2177 - onchange(var).snapshot() 2178 2179 The 'onchange(var).snapshot()' hist trigger action is invoked 2180 whenever the value of 'var' associated with a histogram entry 2181 changes. 2182 2183 The end result is that a global snapshot of the trace buffer will 2184 be saved in the tracing/snapshot file if 'var' changes for any 2185 hist trigger entry. 2186 2187 Note that in this case the changed value is a global variable 2188 associated withe current trace instance. The key of the specific 2189 trace event that caused the value to change and the global value 2190 itself are displayed, along with a message stating that a snapshot 2191 has been taken and where to find it. The user can use the key 2192 information displayed to locate the corresponding bucket in the 2193 histogram for even more detail. 2194 2195 As an example the below defines a hist trigger on the tcp_probe 2196 event, keyed on dport. Whenever a tcp_probe event occurs, the 2197 cwnd field is checked against the current value stored in the 2198 $cwnd variable. If the value has changed, a snapshot is taken. 2199 As part of the setup, all the scheduler and tcp events are also 2200 enabled, which are the events that will show up in the snapshot 2201 when it is taken at some point: 2202 2203 # echo 1 > /sys/kernel/debug/tracing/events/sched/enable 2204 # echo 1 > /sys/kernel/debug/tracing/events/tcp/enable 2205 2206 # echo 'hist:keys=dport:cwnd=snd_cwnd: \ 2207 onchange($cwnd).save(snd_wnd,srtt,rcv_wnd): \ 2208 onchange($cwnd).snapshot()' >> \ 2209 /sys/kernel/debug/tracing/events/tcp/tcp_probe/trigger 2210 2211 When the histogram is displayed, for each bucket the tracked value 2212 and the saved values corresponding to that value are displayed 2213 following the rest of the fields. 2214 2215 If a snaphot was taken, there is also a message indicating that, 2216 along with the value and event that triggered the snapshot: 2217 2218 # cat /sys/kernel/debug/tracing/events/tcp/tcp_probe/hist 2219 { dport: 1521 } hitcount: 8 2220 changed: 10 snd_wnd: 35456 srtt: 154262 rcv_wnd: 42112 2221 2222 { dport: 80 } hitcount: 23 2223 changed: 10 snd_wnd: 28960 srtt: 19604 rcv_wnd: 29312 2224 2225 { dport: 9001 } hitcount: 172 2226 changed: 10 snd_wnd: 48384 srtt: 260444 rcv_wnd: 55168 2227 2228 { dport: 443 } hitcount: 211 2229 changed: 10 snd_wnd: 26960 srtt: 17379 rcv_wnd: 28800 2230 2231 Snapshot taken (see tracing/snapshot). Details: 2232 triggering value { onchange($cwnd) }: 10 2233 triggered by event with key: { dport: 80 } 2234 2235 Totals: 2236 Hits: 414 2237 Entries: 4 2238 Dropped: 0 2239 2240 In the above case, the event that triggered the snapshot has the 2241 key with dport == 80. If you look at the bucket that has 80 as 2242 the key, you'll find the additional values save()'d along with the 2243 changed value for that bucket, which should be the same as the 2244 global changed value (since that was the same value that triggered 2245 the global snapshot). 2246 2247 And finally, looking at the snapshot data should show at or near 2248 the end the event that triggered the snapshot: 2249 2250 # cat /sys/kernel/debug/tracing/snapshot 2251 2252 gnome-shell-1261 [006] dN.3 49.823113: sched_stat_runtime: comm=gnome-shell pid=1261 runtime=49347 [ns] vruntime=1835730389 [ns] 2253 kworker/u16:4-773 [003] d..3 49.823114: sched_switch: prev_comm=kworker/u16:4 prev_pid=773 prev_prio=120 prev_state=R+ ==> next_comm=kworker/3:2 next_pid=135 next_prio=120 2254 gnome-shell-1261 [006] d..3 49.823114: sched_switch: prev_comm=gnome-shell prev_pid=1261 prev_prio=120 prev_state=R+ ==> next_comm=kworker/6:2 next_pid=387 next_prio=120 2255 kworker/3:2-135 [003] d..3 49.823118: sched_stat_runtime: comm=kworker/3:2 pid=135 runtime=5339 [ns] vruntime=17815800388 [ns] 2256 kworker/6:2-387 [006] d..3 49.823120: sched_stat_runtime: comm=kworker/6:2 pid=387 runtime=9594 [ns] vruntime=14589605367 [ns] 2257 kworker/6:2-387 [006] d..3 49.823122: sched_switch: prev_comm=kworker/6:2 prev_pid=387 prev_prio=120 prev_state=R+ ==> next_comm=gnome-shell next_pid=1261 next_prio=120 2258 kworker/3:2-135 [003] d..3 49.823123: sched_switch: prev_comm=kworker/3:2 prev_pid=135 prev_prio=120 prev_state=T ==> next_comm=swapper/3 next_pid=0 next_prio=120 2259 <idle>-0 [004] ..s7 49.823798: tcp_probe: src=10.0.0.10:54326 dest=23.215.104.193:80 mark=0x0 length=32 snd_nxt=0xe3ae2ff5 snd_una=0xe3ae2ecd snd_cwnd=10 ssthresh=2147483647 snd_wnd=28960 srtt=19604 rcv_wnd=29312 2260 22613. User space creating a trigger 2262-------------------------------- 2263 2264Writing into /sys/kernel/tracing/trace_marker writes into the ftrace 2265ring buffer. This can also act like an event, by writing into the trigger 2266file located in /sys/kernel/tracing/events/ftrace/print/ 2267 2268Modifying cyclictest to write into the trace_marker file before it sleeps 2269and after it wakes up, something like this:: 2270 2271 static void traceputs(char *str) 2272 { 2273 /* tracemark_fd is the trace_marker file descriptor */ 2274 if (tracemark_fd < 0) 2275 return; 2276 /* write the tracemark message */ 2277 write(tracemark_fd, str, strlen(str)); 2278 } 2279 2280And later add something like:: 2281 2282 traceputs("start"); 2283 clock_nanosleep(...); 2284 traceputs("end"); 2285 2286We can make a histogram from this:: 2287 2288 # cd /sys/kernel/tracing 2289 # echo 'latency u64 lat' > synthetic_events 2290 # echo 'hist:keys=common_pid:ts0=common_timestamp.usecs if buf == "start"' > events/ftrace/print/trigger 2291 # echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(ftrace.print).latency($lat) if buf == "end"' >> events/ftrace/print/trigger 2292 # echo 'hist:keys=lat,common_pid:sort=lat' > events/synthetic/latency/trigger 2293 2294The above created a synthetic event called "latency" and two histograms 2295against the trace_marker, one gets triggered when "start" is written into the 2296trace_marker file and the other when "end" is written. If the pids match, then 2297it will call the "latency" synthetic event with the calculated latency as its 2298parameter. Finally, a histogram is added to the latency synthetic event to 2299record the calculated latency along with the pid. 2300 2301Now running cyclictest with:: 2302 2303 # ./cyclictest -p80 -d0 -i250 -n -a -t --tracemark -b 1000 2304 2305 -p80 : run threads at priority 80 2306 -d0 : have all threads run at the same interval 2307 -i250 : start the interval at 250 microseconds (all threads will do this) 2308 -n : sleep with nanosleep 2309 -a : affine all threads to a separate CPU 2310 -t : one thread per available CPU 2311 --tracemark : enable trace mark writing 2312 -b 1000 : stop if any latency is greater than 1000 microseconds 2313 2314Note, the -b 1000 is used just to make --tracemark available. 2315 2316Then we can see the histogram created by this with:: 2317 2318 # cat events/synthetic/latency/hist 2319 # event histogram 2320 # 2321 # trigger info: hist:keys=lat,common_pid:vals=hitcount:sort=lat:size=2048 [active] 2322 # 2323 2324 { lat: 107, common_pid: 2039 } hitcount: 1 2325 { lat: 122, common_pid: 2041 } hitcount: 1 2326 { lat: 166, common_pid: 2039 } hitcount: 1 2327 { lat: 174, common_pid: 2039 } hitcount: 1 2328 { lat: 194, common_pid: 2041 } hitcount: 1 2329 { lat: 196, common_pid: 2036 } hitcount: 1 2330 { lat: 197, common_pid: 2038 } hitcount: 1 2331 { lat: 198, common_pid: 2039 } hitcount: 1 2332 { lat: 199, common_pid: 2039 } hitcount: 1 2333 { lat: 200, common_pid: 2041 } hitcount: 1 2334 { lat: 201, common_pid: 2039 } hitcount: 2 2335 { lat: 202, common_pid: 2038 } hitcount: 1 2336 { lat: 202, common_pid: 2043 } hitcount: 1 2337 { lat: 203, common_pid: 2039 } hitcount: 1 2338 { lat: 203, common_pid: 2036 } hitcount: 1 2339 { lat: 203, common_pid: 2041 } hitcount: 1 2340 { lat: 206, common_pid: 2038 } hitcount: 2 2341 { lat: 207, common_pid: 2039 } hitcount: 1 2342 { lat: 207, common_pid: 2036 } hitcount: 1 2343 { lat: 208, common_pid: 2040 } hitcount: 1 2344 { lat: 209, common_pid: 2043 } hitcount: 1 2345 { lat: 210, common_pid: 2039 } hitcount: 1 2346 { lat: 211, common_pid: 2039 } hitcount: 4 2347 { lat: 212, common_pid: 2043 } hitcount: 1 2348 { lat: 212, common_pid: 2039 } hitcount: 2 2349 { lat: 213, common_pid: 2039 } hitcount: 1 2350 { lat: 214, common_pid: 2038 } hitcount: 1 2351 { lat: 214, common_pid: 2039 } hitcount: 2 2352 { lat: 214, common_pid: 2042 } hitcount: 1 2353 { lat: 215, common_pid: 2039 } hitcount: 1 2354 { lat: 217, common_pid: 2036 } hitcount: 1 2355 { lat: 217, common_pid: 2040 } hitcount: 1 2356 { lat: 217, common_pid: 2039 } hitcount: 1 2357 { lat: 218, common_pid: 2039 } hitcount: 6 2358 { lat: 219, common_pid: 2039 } hitcount: 9 2359 { lat: 220, common_pid: 2039 } hitcount: 11 2360 { lat: 221, common_pid: 2039 } hitcount: 5 2361 { lat: 221, common_pid: 2042 } hitcount: 1 2362 { lat: 222, common_pid: 2039 } hitcount: 7 2363 { lat: 223, common_pid: 2036 } hitcount: 1 2364 { lat: 223, common_pid: 2039 } hitcount: 3 2365 { lat: 224, common_pid: 2039 } hitcount: 4 2366 { lat: 224, common_pid: 2037 } hitcount: 1 2367 { lat: 224, common_pid: 2036 } hitcount: 2 2368 { lat: 225, common_pid: 2039 } hitcount: 5 2369 { lat: 225, common_pid: 2042 } hitcount: 1 2370 { lat: 226, common_pid: 2039 } hitcount: 7 2371 { lat: 226, common_pid: 2036 } hitcount: 4 2372 { lat: 227, common_pid: 2039 } hitcount: 6 2373 { lat: 227, common_pid: 2036 } hitcount: 12 2374 { lat: 227, common_pid: 2043 } hitcount: 1 2375 { lat: 228, common_pid: 2039 } hitcount: 7 2376 { lat: 228, common_pid: 2036 } hitcount: 14 2377 { lat: 229, common_pid: 2039 } hitcount: 9 2378 { lat: 229, common_pid: 2036 } hitcount: 8 2379 { lat: 229, common_pid: 2038 } hitcount: 1 2380 { lat: 230, common_pid: 2039 } hitcount: 11 2381 { lat: 230, common_pid: 2036 } hitcount: 6 2382 { lat: 230, common_pid: 2043 } hitcount: 1 2383 { lat: 230, common_pid: 2042 } hitcount: 2 2384 { lat: 231, common_pid: 2041 } hitcount: 1 2385 { lat: 231, common_pid: 2036 } hitcount: 6 2386 { lat: 231, common_pid: 2043 } hitcount: 1 2387 { lat: 231, common_pid: 2039 } hitcount: 8 2388 { lat: 232, common_pid: 2037 } hitcount: 1 2389 { lat: 232, common_pid: 2039 } hitcount: 6 2390 { lat: 232, common_pid: 2040 } hitcount: 2 2391 { lat: 232, common_pid: 2036 } hitcount: 5 2392 { lat: 232, common_pid: 2043 } hitcount: 1 2393 { lat: 233, common_pid: 2036 } hitcount: 5 2394 { lat: 233, common_pid: 2039 } hitcount: 11 2395 { lat: 234, common_pid: 2039 } hitcount: 4 2396 { lat: 234, common_pid: 2038 } hitcount: 2 2397 { lat: 234, common_pid: 2043 } hitcount: 2 2398 { lat: 234, common_pid: 2036 } hitcount: 11 2399 { lat: 234, common_pid: 2040 } hitcount: 1 2400 { lat: 235, common_pid: 2037 } hitcount: 2 2401 { lat: 235, common_pid: 2036 } hitcount: 8 2402 { lat: 235, common_pid: 2043 } hitcount: 2 2403 { lat: 235, common_pid: 2039 } hitcount: 5 2404 { lat: 235, common_pid: 2042 } hitcount: 2 2405 { lat: 235, common_pid: 2040 } hitcount: 4 2406 { lat: 235, common_pid: 2041 } hitcount: 1 2407 { lat: 236, common_pid: 2036 } hitcount: 7 2408 { lat: 236, common_pid: 2037 } hitcount: 1 2409 { lat: 236, common_pid: 2041 } hitcount: 5 2410 { lat: 236, common_pid: 2039 } hitcount: 3 2411 { lat: 236, common_pid: 2043 } hitcount: 9 2412 { lat: 236, common_pid: 2040 } hitcount: 7 2413 { lat: 237, common_pid: 2037 } hitcount: 1 2414 { lat: 237, common_pid: 2040 } hitcount: 1 2415 { lat: 237, common_pid: 2036 } hitcount: 9 2416 { lat: 237, common_pid: 2039 } hitcount: 3 2417 { lat: 237, common_pid: 2043 } hitcount: 8 2418 { lat: 237, common_pid: 2042 } hitcount: 2 2419 { lat: 237, common_pid: 2041 } hitcount: 2 2420 { lat: 238, common_pid: 2043 } hitcount: 10 2421 { lat: 238, common_pid: 2040 } hitcount: 1 2422 { lat: 238, common_pid: 2037 } hitcount: 9 2423 { lat: 238, common_pid: 2038 } hitcount: 1 2424 { lat: 238, common_pid: 2039 } hitcount: 1 2425 { lat: 238, common_pid: 2042 } hitcount: 3 2426 { lat: 238, common_pid: 2036 } hitcount: 7 2427 { lat: 239, common_pid: 2041 } hitcount: 1 2428 { lat: 239, common_pid: 2043 } hitcount: 11 2429 { lat: 239, common_pid: 2037 } hitcount: 11 2430 { lat: 239, common_pid: 2038 } hitcount: 6 2431 { lat: 239, common_pid: 2036 } hitcount: 7 2432 { lat: 239, common_pid: 2040 } hitcount: 1 2433 { lat: 239, common_pid: 2042 } hitcount: 9 2434 { lat: 240, common_pid: 2037 } hitcount: 29 2435 { lat: 240, common_pid: 2043 } hitcount: 15 2436 { lat: 240, common_pid: 2040 } hitcount: 44 2437 { lat: 240, common_pid: 2039 } hitcount: 1 2438 { lat: 240, common_pid: 2041 } hitcount: 2 2439 { lat: 240, common_pid: 2038 } hitcount: 1 2440 { lat: 240, common_pid: 2036 } hitcount: 10 2441 { lat: 240, common_pid: 2042 } hitcount: 13 2442 { lat: 241, common_pid: 2036 } hitcount: 21 2443 { lat: 241, common_pid: 2041 } hitcount: 36 2444 { lat: 241, common_pid: 2037 } hitcount: 34 2445 { lat: 241, common_pid: 2042 } hitcount: 14 2446 { lat: 241, common_pid: 2040 } hitcount: 94 2447 { lat: 241, common_pid: 2039 } hitcount: 12 2448 { lat: 241, common_pid: 2038 } hitcount: 2 2449 { lat: 241, common_pid: 2043 } hitcount: 28 2450 { lat: 242, common_pid: 2040 } hitcount: 109 2451 { lat: 242, common_pid: 2041 } hitcount: 506 2452 { lat: 242, common_pid: 2039 } hitcount: 155 2453 { lat: 242, common_pid: 2042 } hitcount: 21 2454 { lat: 242, common_pid: 2037 } hitcount: 52 2455 { lat: 242, common_pid: 2043 } hitcount: 21 2456 { lat: 242, common_pid: 2036 } hitcount: 16 2457 { lat: 242, common_pid: 2038 } hitcount: 156 2458 { lat: 243, common_pid: 2037 } hitcount: 46 2459 { lat: 243, common_pid: 2039 } hitcount: 40 2460 { lat: 243, common_pid: 2042 } hitcount: 119 2461 { lat: 243, common_pid: 2041 } hitcount: 611 2462 { lat: 243, common_pid: 2036 } hitcount: 69 2463 { lat: 243, common_pid: 2038 } hitcount: 784 2464 { lat: 243, common_pid: 2040 } hitcount: 323 2465 { lat: 243, common_pid: 2043 } hitcount: 14 2466 { lat: 244, common_pid: 2043 } hitcount: 35 2467 { lat: 244, common_pid: 2042 } hitcount: 305 2468 { lat: 244, common_pid: 2039 } hitcount: 8 2469 { lat: 244, common_pid: 2040 } hitcount: 4515 2470 { lat: 244, common_pid: 2038 } hitcount: 371 2471 { lat: 244, common_pid: 2037 } hitcount: 31 2472 { lat: 244, common_pid: 2036 } hitcount: 114 2473 { lat: 244, common_pid: 2041 } hitcount: 3396 2474 { lat: 245, common_pid: 2036 } hitcount: 700 2475 { lat: 245, common_pid: 2041 } hitcount: 2772 2476 { lat: 245, common_pid: 2037 } hitcount: 268 2477 { lat: 245, common_pid: 2039 } hitcount: 472 2478 { lat: 245, common_pid: 2038 } hitcount: 2758 2479 { lat: 245, common_pid: 2042 } hitcount: 3833 2480 { lat: 245, common_pid: 2040 } hitcount: 3105 2481 { lat: 245, common_pid: 2043 } hitcount: 645 2482 { lat: 246, common_pid: 2038 } hitcount: 3451 2483 { lat: 246, common_pid: 2041 } hitcount: 142 2484 { lat: 246, common_pid: 2037 } hitcount: 5101 2485 { lat: 246, common_pid: 2040 } hitcount: 68 2486 { lat: 246, common_pid: 2043 } hitcount: 5099 2487 { lat: 246, common_pid: 2039 } hitcount: 5608 2488 { lat: 246, common_pid: 2042 } hitcount: 3723 2489 { lat: 246, common_pid: 2036 } hitcount: 4738 2490 { lat: 247, common_pid: 2042 } hitcount: 312 2491 { lat: 247, common_pid: 2043 } hitcount: 2385 2492 { lat: 247, common_pid: 2041 } hitcount: 452 2493 { lat: 247, common_pid: 2038 } hitcount: 792 2494 { lat: 247, common_pid: 2040 } hitcount: 78 2495 { lat: 247, common_pid: 2036 } hitcount: 2375 2496 { lat: 247, common_pid: 2039 } hitcount: 1834 2497 { lat: 247, common_pid: 2037 } hitcount: 2655 2498 { lat: 248, common_pid: 2037 } hitcount: 36 2499 { lat: 248, common_pid: 2042 } hitcount: 11 2500 { lat: 248, common_pid: 2038 } hitcount: 122 2501 { lat: 248, common_pid: 2036 } hitcount: 135 2502 { lat: 248, common_pid: 2039 } hitcount: 26 2503 { lat: 248, common_pid: 2041 } hitcount: 503 2504 { lat: 248, common_pid: 2043 } hitcount: 66 2505 { lat: 248, common_pid: 2040 } hitcount: 46 2506 { lat: 249, common_pid: 2037 } hitcount: 29 2507 { lat: 249, common_pid: 2038 } hitcount: 1 2508 { lat: 249, common_pid: 2043 } hitcount: 29 2509 { lat: 249, common_pid: 2039 } hitcount: 8 2510 { lat: 249, common_pid: 2042 } hitcount: 56 2511 { lat: 249, common_pid: 2040 } hitcount: 27 2512 { lat: 249, common_pid: 2041 } hitcount: 11 2513 { lat: 249, common_pid: 2036 } hitcount: 27 2514 { lat: 250, common_pid: 2038 } hitcount: 1 2515 { lat: 250, common_pid: 2036 } hitcount: 30 2516 { lat: 250, common_pid: 2040 } hitcount: 19 2517 { lat: 250, common_pid: 2043 } hitcount: 22 2518 { lat: 250, common_pid: 2042 } hitcount: 20 2519 { lat: 250, common_pid: 2041 } hitcount: 1 2520 { lat: 250, common_pid: 2039 } hitcount: 6 2521 { lat: 250, common_pid: 2037 } hitcount: 48 2522 { lat: 251, common_pid: 2037 } hitcount: 43 2523 { lat: 251, common_pid: 2039 } hitcount: 1 2524 { lat: 251, common_pid: 2036 } hitcount: 12 2525 { lat: 251, common_pid: 2042 } hitcount: 2 2526 { lat: 251, common_pid: 2041 } hitcount: 1 2527 { lat: 251, common_pid: 2043 } hitcount: 15 2528 { lat: 251, common_pid: 2040 } hitcount: 3 2529 { lat: 252, common_pid: 2040 } hitcount: 1 2530 { lat: 252, common_pid: 2036 } hitcount: 12 2531 { lat: 252, common_pid: 2037 } hitcount: 21 2532 { lat: 252, common_pid: 2043 } hitcount: 14 2533 { lat: 253, common_pid: 2037 } hitcount: 21 2534 { lat: 253, common_pid: 2039 } hitcount: 2 2535 { lat: 253, common_pid: 2036 } hitcount: 9 2536 { lat: 253, common_pid: 2043 } hitcount: 6 2537 { lat: 253, common_pid: 2040 } hitcount: 1 2538 { lat: 254, common_pid: 2036 } hitcount: 8 2539 { lat: 254, common_pid: 2043 } hitcount: 3 2540 { lat: 254, common_pid: 2041 } hitcount: 1 2541 { lat: 254, common_pid: 2042 } hitcount: 1 2542 { lat: 254, common_pid: 2039 } hitcount: 1 2543 { lat: 254, common_pid: 2037 } hitcount: 12 2544 { lat: 255, common_pid: 2043 } hitcount: 1 2545 { lat: 255, common_pid: 2037 } hitcount: 2 2546 { lat: 255, common_pid: 2036 } hitcount: 2 2547 { lat: 255, common_pid: 2039 } hitcount: 8 2548 { lat: 256, common_pid: 2043 } hitcount: 1 2549 { lat: 256, common_pid: 2036 } hitcount: 4 2550 { lat: 256, common_pid: 2039 } hitcount: 6 2551 { lat: 257, common_pid: 2039 } hitcount: 5 2552 { lat: 257, common_pid: 2036 } hitcount: 4 2553 { lat: 258, common_pid: 2039 } hitcount: 5 2554 { lat: 258, common_pid: 2036 } hitcount: 2 2555 { lat: 259, common_pid: 2036 } hitcount: 7 2556 { lat: 259, common_pid: 2039 } hitcount: 7 2557 { lat: 260, common_pid: 2036 } hitcount: 8 2558 { lat: 260, common_pid: 2039 } hitcount: 6 2559 { lat: 261, common_pid: 2036 } hitcount: 5 2560 { lat: 261, common_pid: 2039 } hitcount: 7 2561 { lat: 262, common_pid: 2039 } hitcount: 5 2562 { lat: 262, common_pid: 2036 } hitcount: 5 2563 { lat: 263, common_pid: 2039 } hitcount: 7 2564 { lat: 263, common_pid: 2036 } hitcount: 7 2565 { lat: 264, common_pid: 2039 } hitcount: 9 2566 { lat: 264, common_pid: 2036 } hitcount: 9 2567 { lat: 265, common_pid: 2036 } hitcount: 5 2568 { lat: 265, common_pid: 2039 } hitcount: 1 2569 { lat: 266, common_pid: 2036 } hitcount: 1 2570 { lat: 266, common_pid: 2039 } hitcount: 3 2571 { lat: 267, common_pid: 2036 } hitcount: 1 2572 { lat: 267, common_pid: 2039 } hitcount: 3 2573 { lat: 268, common_pid: 2036 } hitcount: 1 2574 { lat: 268, common_pid: 2039 } hitcount: 6 2575 { lat: 269, common_pid: 2036 } hitcount: 1 2576 { lat: 269, common_pid: 2043 } hitcount: 1 2577 { lat: 269, common_pid: 2039 } hitcount: 2 2578 { lat: 270, common_pid: 2040 } hitcount: 1 2579 { lat: 270, common_pid: 2039 } hitcount: 6 2580 { lat: 271, common_pid: 2041 } hitcount: 1 2581 { lat: 271, common_pid: 2039 } hitcount: 5 2582 { lat: 272, common_pid: 2039 } hitcount: 10 2583 { lat: 273, common_pid: 2039 } hitcount: 8 2584 { lat: 274, common_pid: 2039 } hitcount: 2 2585 { lat: 275, common_pid: 2039 } hitcount: 1 2586 { lat: 276, common_pid: 2039 } hitcount: 2 2587 { lat: 276, common_pid: 2037 } hitcount: 1 2588 { lat: 276, common_pid: 2038 } hitcount: 1 2589 { lat: 277, common_pid: 2039 } hitcount: 1 2590 { lat: 277, common_pid: 2042 } hitcount: 1 2591 { lat: 278, common_pid: 2039 } hitcount: 1 2592 { lat: 279, common_pid: 2039 } hitcount: 4 2593 { lat: 279, common_pid: 2043 } hitcount: 1 2594 { lat: 280, common_pid: 2039 } hitcount: 3 2595 { lat: 283, common_pid: 2036 } hitcount: 2 2596 { lat: 284, common_pid: 2039 } hitcount: 1 2597 { lat: 284, common_pid: 2043 } hitcount: 1 2598 { lat: 288, common_pid: 2039 } hitcount: 1 2599 { lat: 289, common_pid: 2039 } hitcount: 1 2600 { lat: 300, common_pid: 2039 } hitcount: 1 2601 { lat: 384, common_pid: 2039 } hitcount: 1 2602 2603 Totals: 2604 Hits: 67625 2605 Entries: 278 2606 Dropped: 0 2607 2608Note, the writes are around the sleep, so ideally they will all be of 250 2609microseconds. If you are wondering how there are several that are under 2610250 microseconds, that is because the way cyclictest works, is if one 2611iteration comes in late, the next one will set the timer to wake up less that 2612250. That is, if an iteration came in 50 microseconds late, the next wake up 2613will be at 200 microseconds. 2614 2615But this could easily be done in userspace. To make this even more 2616interesting, we can mix the histogram between events that happened in the 2617kernel with trace_marker:: 2618 2619 # cd /sys/kernel/tracing 2620 # echo 'latency u64 lat' > synthetic_events 2621 # echo 'hist:keys=pid:ts0=common_timestamp.usecs' > events/sched/sched_waking/trigger 2622 # echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_waking).latency($lat) if buf == "end"' > events/ftrace/print/trigger 2623 # echo 'hist:keys=lat,common_pid:sort=lat' > events/synthetic/latency/trigger 2624 2625The difference this time is that instead of using the trace_marker to start 2626the latency, the sched_waking event is used, matching the common_pid for the 2627trace_marker write with the pid that is being woken by sched_waking. 2628 2629After running cyclictest again with the same parameters, we now have:: 2630 2631 # cat events/synthetic/latency/hist 2632 # event histogram 2633 # 2634 # trigger info: hist:keys=lat,common_pid:vals=hitcount:sort=lat:size=2048 [active] 2635 # 2636 2637 { lat: 7, common_pid: 2302 } hitcount: 640 2638 { lat: 7, common_pid: 2299 } hitcount: 42 2639 { lat: 7, common_pid: 2303 } hitcount: 18 2640 { lat: 7, common_pid: 2305 } hitcount: 166 2641 { lat: 7, common_pid: 2306 } hitcount: 1 2642 { lat: 7, common_pid: 2301 } hitcount: 91 2643 { lat: 7, common_pid: 2300 } hitcount: 17 2644 { lat: 8, common_pid: 2303 } hitcount: 8296 2645 { lat: 8, common_pid: 2304 } hitcount: 6864 2646 { lat: 8, common_pid: 2305 } hitcount: 9464 2647 { lat: 8, common_pid: 2301 } hitcount: 9213 2648 { lat: 8, common_pid: 2306 } hitcount: 6246 2649 { lat: 8, common_pid: 2302 } hitcount: 8797 2650 { lat: 8, common_pid: 2299 } hitcount: 8771 2651 { lat: 8, common_pid: 2300 } hitcount: 8119 2652 { lat: 9, common_pid: 2305 } hitcount: 1519 2653 { lat: 9, common_pid: 2299 } hitcount: 2346 2654 { lat: 9, common_pid: 2303 } hitcount: 2841 2655 { lat: 9, common_pid: 2301 } hitcount: 1846 2656 { lat: 9, common_pid: 2304 } hitcount: 3861 2657 { lat: 9, common_pid: 2302 } hitcount: 1210 2658 { lat: 9, common_pid: 2300 } hitcount: 2762 2659 { lat: 9, common_pid: 2306 } hitcount: 4247 2660 { lat: 10, common_pid: 2299 } hitcount: 16 2661 { lat: 10, common_pid: 2306 } hitcount: 333 2662 { lat: 10, common_pid: 2303 } hitcount: 16 2663 { lat: 10, common_pid: 2304 } hitcount: 168 2664 { lat: 10, common_pid: 2302 } hitcount: 240 2665 { lat: 10, common_pid: 2301 } hitcount: 28 2666 { lat: 10, common_pid: 2300 } hitcount: 95 2667 { lat: 10, common_pid: 2305 } hitcount: 18 2668 { lat: 11, common_pid: 2303 } hitcount: 5 2669 { lat: 11, common_pid: 2305 } hitcount: 8 2670 { lat: 11, common_pid: 2306 } hitcount: 221 2671 { lat: 11, common_pid: 2302 } hitcount: 76 2672 { lat: 11, common_pid: 2304 } hitcount: 26 2673 { lat: 11, common_pid: 2300 } hitcount: 125 2674 { lat: 11, common_pid: 2299 } hitcount: 2 2675 { lat: 12, common_pid: 2305 } hitcount: 3 2676 { lat: 12, common_pid: 2300 } hitcount: 6 2677 { lat: 12, common_pid: 2306 } hitcount: 90 2678 { lat: 12, common_pid: 2302 } hitcount: 4 2679 { lat: 12, common_pid: 2303 } hitcount: 1 2680 { lat: 12, common_pid: 2304 } hitcount: 122 2681 { lat: 13, common_pid: 2300 } hitcount: 12 2682 { lat: 13, common_pid: 2301 } hitcount: 1 2683 { lat: 13, common_pid: 2306 } hitcount: 32 2684 { lat: 13, common_pid: 2302 } hitcount: 5 2685 { lat: 13, common_pid: 2305 } hitcount: 1 2686 { lat: 13, common_pid: 2303 } hitcount: 1 2687 { lat: 13, common_pid: 2304 } hitcount: 61 2688 { lat: 14, common_pid: 2303 } hitcount: 4 2689 { lat: 14, common_pid: 2306 } hitcount: 5 2690 { lat: 14, common_pid: 2305 } hitcount: 4 2691 { lat: 14, common_pid: 2304 } hitcount: 62 2692 { lat: 14, common_pid: 2302 } hitcount: 19 2693 { lat: 14, common_pid: 2300 } hitcount: 33 2694 { lat: 14, common_pid: 2299 } hitcount: 1 2695 { lat: 14, common_pid: 2301 } hitcount: 4 2696 { lat: 15, common_pid: 2305 } hitcount: 1 2697 { lat: 15, common_pid: 2302 } hitcount: 25 2698 { lat: 15, common_pid: 2300 } hitcount: 11 2699 { lat: 15, common_pid: 2299 } hitcount: 5 2700 { lat: 15, common_pid: 2301 } hitcount: 1 2701 { lat: 15, common_pid: 2304 } hitcount: 8 2702 { lat: 15, common_pid: 2303 } hitcount: 1 2703 { lat: 15, common_pid: 2306 } hitcount: 6 2704 { lat: 16, common_pid: 2302 } hitcount: 31 2705 { lat: 16, common_pid: 2306 } hitcount: 3 2706 { lat: 16, common_pid: 2300 } hitcount: 5 2707 { lat: 17, common_pid: 2302 } hitcount: 6 2708 { lat: 17, common_pid: 2303 } hitcount: 1 2709 { lat: 18, common_pid: 2304 } hitcount: 1 2710 { lat: 18, common_pid: 2302 } hitcount: 8 2711 { lat: 18, common_pid: 2299 } hitcount: 1 2712 { lat: 18, common_pid: 2301 } hitcount: 1 2713 { lat: 19, common_pid: 2303 } hitcount: 4 2714 { lat: 19, common_pid: 2304 } hitcount: 5 2715 { lat: 19, common_pid: 2302 } hitcount: 4 2716 { lat: 19, common_pid: 2299 } hitcount: 3 2717 { lat: 19, common_pid: 2306 } hitcount: 1 2718 { lat: 19, common_pid: 2300 } hitcount: 4 2719 { lat: 19, common_pid: 2305 } hitcount: 5 2720 { lat: 20, common_pid: 2299 } hitcount: 2 2721 { lat: 20, common_pid: 2302 } hitcount: 3 2722 { lat: 20, common_pid: 2305 } hitcount: 1 2723 { lat: 20, common_pid: 2300 } hitcount: 2 2724 { lat: 20, common_pid: 2301 } hitcount: 2 2725 { lat: 20, common_pid: 2303 } hitcount: 3 2726 { lat: 21, common_pid: 2305 } hitcount: 1 2727 { lat: 21, common_pid: 2299 } hitcount: 5 2728 { lat: 21, common_pid: 2303 } hitcount: 4 2729 { lat: 21, common_pid: 2302 } hitcount: 7 2730 { lat: 21, common_pid: 2300 } hitcount: 1 2731 { lat: 21, common_pid: 2301 } hitcount: 5 2732 { lat: 21, common_pid: 2304 } hitcount: 2 2733 { lat: 22, common_pid: 2302 } hitcount: 5 2734 { lat: 22, common_pid: 2303 } hitcount: 1 2735 { lat: 22, common_pid: 2306 } hitcount: 3 2736 { lat: 22, common_pid: 2301 } hitcount: 2 2737 { lat: 22, common_pid: 2300 } hitcount: 1 2738 { lat: 22, common_pid: 2299 } hitcount: 1 2739 { lat: 22, common_pid: 2305 } hitcount: 1 2740 { lat: 22, common_pid: 2304 } hitcount: 1 2741 { lat: 23, common_pid: 2299 } hitcount: 1 2742 { lat: 23, common_pid: 2306 } hitcount: 2 2743 { lat: 23, common_pid: 2302 } hitcount: 6 2744 { lat: 24, common_pid: 2302 } hitcount: 3 2745 { lat: 24, common_pid: 2300 } hitcount: 1 2746 { lat: 24, common_pid: 2306 } hitcount: 2 2747 { lat: 24, common_pid: 2305 } hitcount: 1 2748 { lat: 24, common_pid: 2299 } hitcount: 1 2749 { lat: 25, common_pid: 2300 } hitcount: 1 2750 { lat: 25, common_pid: 2302 } hitcount: 4 2751 { lat: 26, common_pid: 2302 } hitcount: 2 2752 { lat: 27, common_pid: 2305 } hitcount: 1 2753 { lat: 27, common_pid: 2300 } hitcount: 1 2754 { lat: 27, common_pid: 2302 } hitcount: 3 2755 { lat: 28, common_pid: 2306 } hitcount: 1 2756 { lat: 28, common_pid: 2302 } hitcount: 4 2757 { lat: 29, common_pid: 2302 } hitcount: 1 2758 { lat: 29, common_pid: 2300 } hitcount: 2 2759 { lat: 29, common_pid: 2306 } hitcount: 1 2760 { lat: 29, common_pid: 2304 } hitcount: 1 2761 { lat: 30, common_pid: 2302 } hitcount: 4 2762 { lat: 31, common_pid: 2302 } hitcount: 6 2763 { lat: 32, common_pid: 2302 } hitcount: 1 2764 { lat: 33, common_pid: 2299 } hitcount: 1 2765 { lat: 33, common_pid: 2302 } hitcount: 3 2766 { lat: 34, common_pid: 2302 } hitcount: 2 2767 { lat: 35, common_pid: 2302 } hitcount: 1 2768 { lat: 35, common_pid: 2304 } hitcount: 1 2769 { lat: 36, common_pid: 2302 } hitcount: 4 2770 { lat: 37, common_pid: 2302 } hitcount: 6 2771 { lat: 38, common_pid: 2302 } hitcount: 2 2772 { lat: 39, common_pid: 2302 } hitcount: 2 2773 { lat: 39, common_pid: 2304 } hitcount: 1 2774 { lat: 40, common_pid: 2304 } hitcount: 2 2775 { lat: 40, common_pid: 2302 } hitcount: 5 2776 { lat: 41, common_pid: 2304 } hitcount: 1 2777 { lat: 41, common_pid: 2302 } hitcount: 8 2778 { lat: 42, common_pid: 2302 } hitcount: 6 2779 { lat: 42, common_pid: 2304 } hitcount: 1 2780 { lat: 43, common_pid: 2302 } hitcount: 3 2781 { lat: 43, common_pid: 2304 } hitcount: 4 2782 { lat: 44, common_pid: 2302 } hitcount: 6 2783 { lat: 45, common_pid: 2302 } hitcount: 5 2784 { lat: 46, common_pid: 2302 } hitcount: 5 2785 { lat: 47, common_pid: 2302 } hitcount: 7 2786 { lat: 48, common_pid: 2301 } hitcount: 1 2787 { lat: 48, common_pid: 2302 } hitcount: 9 2788 { lat: 49, common_pid: 2302 } hitcount: 3 2789 { lat: 50, common_pid: 2302 } hitcount: 1 2790 { lat: 50, common_pid: 2301 } hitcount: 1 2791 { lat: 51, common_pid: 2302 } hitcount: 2 2792 { lat: 51, common_pid: 2301 } hitcount: 1 2793 { lat: 61, common_pid: 2302 } hitcount: 1 2794 { lat: 110, common_pid: 2302 } hitcount: 1 2795 2796 Totals: 2797 Hits: 89565 2798 Entries: 158 2799 Dropped: 0 2800 2801This doesn't tell us any information about how late cyclictest may have 2802woken up, but it does show us a nice histogram of how long it took from 2803the time that cyclictest was woken to the time it made it into user space. 2804