1perf-intel-pt(1) 2================ 3 4NAME 5---- 6perf-intel-pt - Support for Intel Processor Trace within perf tools 7 8SYNOPSIS 9-------- 10[verse] 11'perf record' -e intel_pt// 12 13DESCRIPTION 14----------- 15 16Intel Processor Trace (Intel PT) is an extension of Intel Architecture that 17collects information about software execution such as control flow, execution 18modes and timings and formats it into highly compressed binary packets. 19Technical details are documented in the Intel 64 and IA-32 Architectures 20Software Developer Manuals, Chapter 36 Intel Processor Trace. 21 22Intel PT is first supported in Intel Core M and 5th generation Intel Core 23processors that are based on the Intel micro-architecture code name Broadwell. 24 25Trace data is collected by 'perf record' and stored within the perf.data file. 26See below for options to 'perf record'. 27 28Trace data must be 'decoded' which involves walking the object code and matching 29the trace data packets. For example a TNT packet only tells whether a 30conditional branch was taken or not taken, so to make use of that packet the 31decoder must know precisely which instruction was being executed. 32 33Decoding is done on-the-fly. The decoder outputs samples in the same format as 34samples output by perf hardware events, for example as though the "instructions" 35or "branches" events had been recorded. Presently 3 tools support this: 36'perf script', 'perf report' and 'perf inject'. See below for more information 37on using those tools. 38 39The main distinguishing feature of Intel PT is that the decoder can determine 40the exact flow of software execution. Intel PT can be used to understand why 41and how did software get to a certain point, or behave a certain way. The 42software does not have to be recompiled, so Intel PT works with debug or release 43builds, however the executed images are needed - which makes use in JIT-compiled 44environments, or with self-modified code, a challenge. Also symbols need to be 45provided to make sense of addresses. 46 47A limitation of Intel PT is that it produces huge amounts of trace data 48(hundreds of megabytes per second per core) which takes a long time to decode, 49for example two or three orders of magnitude longer than it took to collect. 50Another limitation is the performance impact of tracing, something that will 51vary depending on the use-case and architecture. 52 53 54Quickstart 55---------- 56 57It is important to start small. That is because it is easy to capture vastly 58more data than can possibly be processed. 59 60The simplest thing to do with Intel PT is userspace profiling of small programs. 61Data is captured with 'perf record' e.g. to trace 'ls' userspace-only: 62 63 perf record -e intel_pt//u ls 64 65And profiled with 'perf report' e.g. 66 67 perf report 68 69To also trace kernel space presents a problem, namely kernel self-modifying 70code. A fairly good kernel image is available in /proc/kcore but to get an 71accurate image a copy of /proc/kcore needs to be made under the same conditions 72as the data capture. 'perf record' can make a copy of /proc/kcore if the option 73--kcore is used, but access to /proc/kcore is restricted e.g. 74 75 sudo perf record -o pt_ls --kcore -e intel_pt// -- ls 76 77which will create a directory named 'pt_ls' and put the perf.data file (named 78simply 'data') and copies of /proc/kcore, /proc/kallsyms and /proc/modules into 79it. The other tools understand the directory format, so to use 'perf report' 80becomes: 81 82 sudo perf report -i pt_ls 83 84Because samples are synthesized after-the-fact, the sampling period can be 85selected for reporting. e.g. sample every microsecond 86 87 sudo perf report pt_ls --itrace=i1usge 88 89See the sections below for more information about the --itrace option. 90 91Beware the smaller the period, the more samples that are produced, and the 92longer it takes to process them. 93 94Also note that the coarseness of Intel PT timing information will start to 95distort the statistical value of the sampling as the sampling period becomes 96smaller. 97 98To represent software control flow, "branches" samples are produced. By default 99a branch sample is synthesized for every single branch. To get an idea what 100data is available you can use the 'perf script' tool with all itrace sampling 101options, which will list all the samples. 102 103 perf record -e intel_pt//u ls 104 perf script --itrace=ibxwpe 105 106An interesting field that is not printed by default is 'flags' which can be 107displayed as follows: 108 109 perf script --itrace=ibxwpe -F+flags 110 111The flags are "bcrosyiABExghDt" which stand for branch, call, return, conditional, 112system, asynchronous, interrupt, transaction abort, trace begin, trace end, 113in transaction, VM-entry, VM-exit, interrupt disabled, and interrupt disable 114toggle respectively. 115 116perf script also supports higher level ways to dump instruction traces: 117 118 perf script --insn-trace --xed 119 120Dump all instructions. This requires installing the xed tool (see XED below) 121Dumping all instructions in a long trace can be fairly slow. It is usually better 122to start with higher level decoding, like 123 124 perf script --call-trace 125 126or 127 128 perf script --call-ret-trace 129 130and then select a time range of interest. The time range can then be examined 131in detail with 132 133 perf script --time starttime,stoptime --insn-trace --xed 134 135While examining the trace it's also useful to filter on specific CPUs using 136the -C option 137 138 perf script --time starttime,stoptime --insn-trace --xed -C 1 139 140Dump all instructions in time range on CPU 1. 141 142Another interesting field that is not printed by default is 'ipc' which can be 143displayed as follows: 144 145 perf script --itrace=be -F+ipc 146 147There are two ways that instructions-per-cycle (IPC) can be calculated depending 148on the recording. 149 150If the 'cyc' config term (see config terms section below) was used, then IPC is 151calculated using the cycle count from CYC packets, otherwise MTC packets are 152used - refer to the 'mtc' config term. When MTC is used, however, the values 153are less accurate because the timing is less accurate. 154 155Because Intel PT does not update the cycle count on every branch or instruction, 156the values will often be zero. When there are values, they will be the number 157of instructions and number of cycles since the last update, and thus represent 158the average IPC since the last IPC for that event type. Note IPC for "branches" 159events is calculated separately from IPC for "instructions" events. 160 161Even with the 'cyc' config term, it is possible to produce IPC information for 162every change of timestamp, but at the expense of accuracy. That is selected by 163specifying the itrace 'A' option. Due to the granularity of timestamps, the 164actual number of cycles increases even though the cycles reported does not. 165The number of instructions is known, but if IPC is reported, cycles can be too 166low and so IPC is too high. Note that inaccuracy decreases as the period of 167sampling increases i.e. if the number of cycles is too low by a small amount, 168that becomes less significant if the number of cycles is large. It may also be 169useful to use the 'A' option in conjunction with dlfilter-show-cycles.so to 170provide higher granularity cycle information. 171 172Also note that the IPC instruction count may or may not include the current 173instruction. If the cycle count is associated with an asynchronous branch 174(e.g. page fault or interrupt), then the instruction count does not include the 175current instruction, otherwise it does. That is consistent with whether or not 176that instruction has retired when the cycle count is updated. 177 178Another note, in the case of "branches" events, non-taken branches are not 179presently sampled, so IPC values for them do not appear e.g. a CYC packet with a 180TNT packet that starts with a non-taken branch. To see every possible IPC 181value, "instructions" events can be used e.g. --itrace=i0ns 182 183While it is possible to create scripts to analyze the data, an alternative 184approach is available to export the data to a sqlite or postgresql database. 185Refer to script export-to-sqlite.py or export-to-postgresql.py for more details, 186and to script exported-sql-viewer.py for an example of using the database. 187 188There is also script intel-pt-events.py which provides an example of how to 189unpack the raw data for power events and PTWRITE. The script also displays 190branches, and supports 2 additional modes selected by option: 191 192 --insn-trace - instruction trace 193 --src-trace - source trace 194 195As mentioned above, it is easy to capture too much data. One way to limit the 196data captured is to use 'snapshot' mode which is explained further below. 197Refer to 'new snapshot option' and 'Intel PT modes of operation' further below. 198 199Another problem that will be experienced is decoder errors. They can be caused 200by inability to access the executed image, self-modified or JIT-ed code, or the 201inability to match side-band information (such as context switches and mmaps) 202which results in the decoder not knowing what code was executed. 203 204There is also the problem of perf not being able to copy the data fast enough, 205resulting in data lost because the buffer was full. See 'Buffer handling' below 206for more details. 207 208 209perf record 210----------- 211 212new event 213~~~~~~~~~ 214 215The Intel PT kernel driver creates a new PMU for Intel PT. PMU events are 216selected by providing the PMU name followed by the "config" separated by slashes. 217An enhancement has been made to allow default "config" e.g. the option 218 219 -e intel_pt// 220 221will use a default config value. Currently that is the same as 222 223 -e intel_pt/tsc,noretcomp=0/ 224 225which is the same as 226 227 -e intel_pt/tsc=1,noretcomp=0/ 228 229Note there are now new config terms - see section 'config terms' further below. 230 231The config terms are listed in /sys/devices/intel_pt/format. They are bit 232fields within the config member of the struct perf_event_attr which is 233passed to the kernel by the perf_event_open system call. They correspond to bit 234fields in the IA32_RTIT_CTL MSR. Here is a list of them and their definitions: 235 236 $ grep -H . /sys/bus/event_source/devices/intel_pt/format/* 237 /sys/bus/event_source/devices/intel_pt/format/cyc:config:1 238 /sys/bus/event_source/devices/intel_pt/format/cyc_thresh:config:19-22 239 /sys/bus/event_source/devices/intel_pt/format/mtc:config:9 240 /sys/bus/event_source/devices/intel_pt/format/mtc_period:config:14-17 241 /sys/bus/event_source/devices/intel_pt/format/noretcomp:config:11 242 /sys/bus/event_source/devices/intel_pt/format/psb_period:config:24-27 243 /sys/bus/event_source/devices/intel_pt/format/tsc:config:10 244 245Note that the default config must be overridden for each term i.e. 246 247 -e intel_pt/noretcomp=0/ 248 249is the same as: 250 251 -e intel_pt/tsc=1,noretcomp=0/ 252 253So, to disable TSC packets use: 254 255 -e intel_pt/tsc=0/ 256 257It is also possible to specify the config value explicitly: 258 259 -e intel_pt/config=0x400/ 260 261Note that, as with all events, the event is suffixed with event modifiers: 262 263 u userspace 264 k kernel 265 h hypervisor 266 G guest 267 H host 268 p precise ip 269 270'h', 'G' and 'H' are for virtualization which are not used by Intel PT. 271'p' is also not relevant to Intel PT. So only options 'u' and 'k' are 272meaningful for Intel PT. 273 274perf_event_attr is displayed if the -vv option is used e.g. 275 276 ------------------------------------------------------------ 277 perf_event_attr: 278 type 6 279 size 112 280 config 0x400 281 { sample_period, sample_freq } 1 282 sample_type IP|TID|TIME|CPU|IDENTIFIER 283 read_format ID 284 disabled 1 285 inherit 1 286 exclude_kernel 1 287 exclude_hv 1 288 enable_on_exec 1 289 sample_id_all 1 290 ------------------------------------------------------------ 291 sys_perf_event_open: pid 31104 cpu 0 group_fd -1 flags 0x8 292 sys_perf_event_open: pid 31104 cpu 1 group_fd -1 flags 0x8 293 sys_perf_event_open: pid 31104 cpu 2 group_fd -1 flags 0x8 294 sys_perf_event_open: pid 31104 cpu 3 group_fd -1 flags 0x8 295 ------------------------------------------------------------ 296 297 298config terms 299~~~~~~~~~~~~ 300 301The June 2015 version of Intel 64 and IA-32 Architectures Software Developer 302Manuals, Chapter 36 Intel Processor Trace, defined new Intel PT features. 303Some of the features are reflect in new config terms. All the config terms are 304described below. 305 306tsc Always supported. Produces TSC timestamp packets to provide 307 timing information. In some cases it is possible to decode 308 without timing information, for example a per-thread context 309 that does not overlap executable memory maps. 310 311 The default config selects tsc (i.e. tsc=1). 312 313noretcomp Always supported. Disables "return compression" so a TIP packet 314 is produced when a function returns. Causes more packets to be 315 produced but might make decoding more reliable. 316 317 The default config does not select noretcomp (i.e. noretcomp=0). 318 319psb_period Allows the frequency of PSB packets to be specified. 320 321 The PSB packet is a synchronization packet that provides a 322 starting point for decoding or recovery from errors. 323 324 Support for psb_period is indicated by: 325 326 /sys/bus/event_source/devices/intel_pt/caps/psb_cyc 327 328 which contains "1" if the feature is supported and "0" 329 otherwise. 330 331 Valid values are given by: 332 333 /sys/bus/event_source/devices/intel_pt/caps/psb_periods 334 335 which contains a hexadecimal value, the bits of which represent 336 valid values e.g. bit 2 set means value 2 is valid. 337 338 The psb_period value is converted to the approximate number of 339 trace bytes between PSB packets as: 340 341 2 ^ (value + 11) 342 343 e.g. value 3 means 16KiB bytes between PSBs 344 345 If an invalid value is entered, the error message 346 will give a list of valid values e.g. 347 348 $ perf record -e intel_pt/psb_period=15/u uname 349 Invalid psb_period for intel_pt. Valid values are: 0-5 350 351 If MTC packets are selected, the default config selects a value 352 of 3 (i.e. psb_period=3) or the nearest lower value that is 353 supported (0 is always supported). Otherwise the default is 0. 354 355 If decoding is expected to be reliable and the buffer is large 356 then a large PSB period can be used. 357 358 Because a TSC packet is produced with PSB, the PSB period can 359 also affect the granularity to timing information in the absence 360 of MTC or CYC. 361 362mtc Produces MTC timing packets. 363 364 MTC packets provide finer grain timestamp information than TSC 365 packets. MTC packets record time using the hardware crystal 366 clock (CTC) which is related to TSC packets using a TMA packet. 367 368 Support for this feature is indicated by: 369 370 /sys/bus/event_source/devices/intel_pt/caps/mtc 371 372 which contains "1" if the feature is supported and 373 "0" otherwise. 374 375 The frequency of MTC packets can also be specified - see 376 mtc_period below. 377 378mtc_period Specifies how frequently MTC packets are produced - see mtc 379 above for how to determine if MTC packets are supported. 380 381 Valid values are given by: 382 383 /sys/bus/event_source/devices/intel_pt/caps/mtc_periods 384 385 which contains a hexadecimal value, the bits of which represent 386 valid values e.g. bit 2 set means value 2 is valid. 387 388 The mtc_period value is converted to the MTC frequency as: 389 390 CTC-frequency / (2 ^ value) 391 392 e.g. value 3 means one eighth of CTC-frequency 393 394 Where CTC is the hardware crystal clock, the frequency of which 395 can be related to TSC via values provided in cpuid leaf 0x15. 396 397 If an invalid value is entered, the error message 398 will give a list of valid values e.g. 399 400 $ perf record -e intel_pt/mtc_period=15/u uname 401 Invalid mtc_period for intel_pt. Valid values are: 0,3,6,9 402 403 The default value is 3 or the nearest lower value 404 that is supported (0 is always supported). 405 406cyc Produces CYC timing packets. 407 408 CYC packets provide even finer grain timestamp information than 409 MTC and TSC packets. A CYC packet contains the number of CPU 410 cycles since the last CYC packet. Unlike MTC and TSC packets, 411 CYC packets are only sent when another packet is also sent. 412 413 Support for this feature is indicated by: 414 415 /sys/bus/event_source/devices/intel_pt/caps/psb_cyc 416 417 which contains "1" if the feature is supported and 418 "0" otherwise. 419 420 The number of CYC packets produced can be reduced by specifying 421 a threshold - see cyc_thresh below. 422 423cyc_thresh Specifies how frequently CYC packets are produced - see cyc 424 above for how to determine if CYC packets are supported. 425 426 Valid cyc_thresh values are given by: 427 428 /sys/bus/event_source/devices/intel_pt/caps/cycle_thresholds 429 430 which contains a hexadecimal value, the bits of which represent 431 valid values e.g. bit 2 set means value 2 is valid. 432 433 The cyc_thresh value represents the minimum number of CPU cycles 434 that must have passed before a CYC packet can be sent. The 435 number of CPU cycles is: 436 437 2 ^ (value - 1) 438 439 e.g. value 4 means 8 CPU cycles must pass before a CYC packet 440 can be sent. Note a CYC packet is still only sent when another 441 packet is sent, not at, e.g. every 8 CPU cycles. 442 443 If an invalid value is entered, the error message 444 will give a list of valid values e.g. 445 446 $ perf record -e intel_pt/cyc,cyc_thresh=15/u uname 447 Invalid cyc_thresh for intel_pt. Valid values are: 0-12 448 449 CYC packets are not requested by default. 450 451pt Specifies pass-through which enables the 'branch' config term. 452 453 The default config selects 'pt' if it is available, so a user will 454 never need to specify this term. 455 456branch Enable branch tracing. Branch tracing is enabled by default so to 457 disable branch tracing use 'branch=0'. 458 459 The default config selects 'branch' if it is available. 460 461ptw Enable PTWRITE packets which are produced when a ptwrite instruction 462 is executed. 463 464 Support for this feature is indicated by: 465 466 /sys/bus/event_source/devices/intel_pt/caps/ptwrite 467 468 which contains "1" if the feature is supported and 469 "0" otherwise. 470 471 As an alternative, refer to "Emulated PTWRITE" further below. 472 473fup_on_ptw Enable a FUP packet to follow the PTWRITE packet. The FUP packet 474 provides the address of the ptwrite instruction. In the absence of 475 fup_on_ptw, the decoder will use the address of the previous branch 476 if branch tracing is enabled, otherwise the address will be zero. 477 Note that fup_on_ptw will work even when branch tracing is disabled. 478 479pwr_evt Enable power events. The power events provide information about 480 changes to the CPU C-state. 481 482 Support for this feature is indicated by: 483 484 /sys/bus/event_source/devices/intel_pt/caps/power_event_trace 485 486 which contains "1" if the feature is supported and 487 "0" otherwise. 488 489event Enable Event Trace. The events provide information about asynchronous 490 events. 491 492 Support for this feature is indicated by: 493 494 /sys/bus/event_source/devices/intel_pt/caps/event_trace 495 496 which contains "1" if the feature is supported and 497 "0" otherwise. 498 499notnt Disable TNT packets. Without TNT packets, it is not possible to walk 500 executable code to reconstruct control flow, however FUP, TIP, TIP.PGE 501 and TIP.PGD packets still indicate asynchronous control flow, and (if 502 return compression is disabled - see noretcomp) return statements. 503 The advantage of eliminating TNT packets is reducing the size of the 504 trace and corresponding tracing overhead. 505 506 Support for this feature is indicated by: 507 508 /sys/bus/event_source/devices/intel_pt/caps/tnt_disable 509 510 which contains "1" if the feature is supported and 511 "0" otherwise. 512 513 514AUX area sampling option 515~~~~~~~~~~~~~~~~~~~~~~~~ 516 517To select Intel PT "sampling" the AUX area sampling option can be used: 518 519 --aux-sample 520 521Optionally it can be followed by the sample size in bytes e.g. 522 523 --aux-sample=8192 524 525In addition, the Intel PT event to sample must be defined e.g. 526 527 -e intel_pt//u 528 529Samples on other events will be created containing Intel PT data e.g. the 530following will create Intel PT samples on the branch-misses event, note the 531events must be grouped using {}: 532 533 perf record --aux-sample -e '{intel_pt//u,branch-misses:u}' 534 535An alternative to '--aux-sample' is to add the config term 'aux-sample-size' to 536events. In this case, the grouping is implied e.g. 537 538 perf record -e intel_pt//u -e branch-misses/aux-sample-size=8192/u 539 540is the same as: 541 542 perf record -e '{intel_pt//u,branch-misses/aux-sample-size=8192/u}' 543 544but allows for also using an address filter e.g.: 545 546 perf record -e intel_pt//u --filter 'filter * @/bin/ls' -e branch-misses/aux-sample-size=8192/u -- ls 547 548It is important to select a sample size that is big enough to contain at least 549one PSB packet. If not a warning will be displayed: 550 551 Intel PT sample size (%zu) may be too small for PSB period (%zu) 552 553The calculation used for that is: if sample_size <= psb_period + 256 display the 554warning. When sampling is used, psb_period defaults to 0 (2KiB). 555 556The default sample size is 4KiB. 557 558The sample size is passed in aux_sample_size in struct perf_event_attr. The 559sample size is limited by the maximum event size which is 64KiB. It is 560difficult to know how big the event might be without the trace sample attached, 561but the tool validates that the sample size is not greater than 60KiB. 562 563 564new snapshot option 565~~~~~~~~~~~~~~~~~~~ 566 567The difference between full trace and snapshot from the kernel's perspective is 568that in full trace we don't overwrite trace data that the user hasn't collected 569yet (and indicated that by advancing aux_tail), whereas in snapshot mode we let 570the trace run and overwrite older data in the buffer so that whenever something 571interesting happens, we can stop it and grab a snapshot of what was going on 572around that interesting moment. 573 574To select snapshot mode a new option has been added: 575 576 -S 577 578Optionally it can be followed by the snapshot size e.g. 579 580 -S0x100000 581 582The default snapshot size is the auxtrace mmap size. If neither auxtrace mmap size 583nor snapshot size is specified, then the default is 4MiB for privileged users 584(or if /proc/sys/kernel/perf_event_paranoid < 0), 128KiB for unprivileged users. 585If an unprivileged user does not specify mmap pages, the mmap pages will be 586reduced as described in the 'new auxtrace mmap size option' section below. 587 588The snapshot size is displayed if the option -vv is used e.g. 589 590 Intel PT snapshot size: %zu 591 592 593new auxtrace mmap size option 594~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 595 596Intel PT buffer size is specified by an addition to the -m option e.g. 597 598 -m,16 599 600selects a buffer size of 16 pages i.e. 64KiB. 601 602Note that the existing functionality of -m is unchanged. The auxtrace mmap size 603is specified by the optional addition of a comma and the value. 604 605The default auxtrace mmap size for Intel PT is 4MiB/page_size for privileged users 606(or if /proc/sys/kernel/perf_event_paranoid < 0), 128KiB for unprivileged users. 607If an unprivileged user does not specify mmap pages, the mmap pages will be 608reduced from the default 512KiB/page_size to 256KiB/page_size, otherwise the 609user is likely to get an error as they exceed their mlock limit (Max locked 610memory as shown in /proc/self/limits). Note that perf does not count the first 611512KiB (actually /proc/sys/kernel/perf_event_mlock_kb minus 1 page) per cpu 612against the mlock limit so an unprivileged user is allowed 512KiB per cpu plus 613their mlock limit (which defaults to 64KiB but is not multiplied by the number 614of cpus). 615 616In full-trace mode, powers of two are allowed for buffer size, with a minimum 617size of 2 pages. In snapshot mode or sampling mode, it is the same but the 618minimum size is 1 page. 619 620The mmap size and auxtrace mmap size are displayed if the -vv option is used e.g. 621 622 mmap length 528384 623 auxtrace mmap length 4198400 624 625 626Intel PT modes of operation 627~~~~~~~~~~~~~~~~~~~~~~~~~~~ 628 629Intel PT can be used in 3 modes: 630 full-trace mode 631 sample mode 632 snapshot mode 633 634Full-trace mode traces continuously e.g. 635 636 perf record -e intel_pt//u uname 637 638Sample mode attaches a Intel PT sample to other events e.g. 639 640 perf record --aux-sample -e intel_pt//u -e branch-misses:u 641 642Snapshot mode captures the available data when a signal is sent or "snapshot" 643control command is issued. e.g. using a signal 644 645 perf record -v -e intel_pt//u -S ./loopy 1000000000 & 646 [1] 11435 647 kill -USR2 11435 648 Recording AUX area tracing snapshot 649 650Note that the signal sent is SIGUSR2. 651Note that "Recording AUX area tracing snapshot" is displayed because the -v 652option is used. 653 654The advantage of using "snapshot" control command is that the access is 655controlled by access to a FIFO e.g. 656 657 $ mkfifo perf.control 658 $ mkfifo perf.ack 659 $ cat perf.ack & 660 [1] 15235 661 $ sudo ~/bin/perf record --control fifo:perf.control,perf.ack -S -e intel_pt//u -- sleep 60 & 662 [2] 15243 663 $ ps -e | grep perf 664 15244 pts/1 00:00:00 perf 665 $ kill -USR2 15244 666 bash: kill: (15244) - Operation not permitted 667 $ echo snapshot > perf.control 668 ack 669 670The 3 Intel PT modes of operation cannot be used together. 671 672 673Buffer handling 674~~~~~~~~~~~~~~~ 675 676There may be buffer limitations (i.e. single ToPa entry) which means that actual 677buffer sizes are limited to powers of 2 up to 4MiB (MAX_ORDER). In order to 678provide other sizes, and in particular an arbitrarily large size, multiple 679buffers are logically concatenated. However an interrupt must be used to switch 680between buffers. That has two potential problems: 681 a) the interrupt may not be handled in time so that the current buffer 682 becomes full and some trace data is lost. 683 b) the interrupts may slow the system and affect the performance 684 results. 685 686If trace data is lost, the driver sets 'truncated' in the PERF_RECORD_AUX event 687which the tools report as an error. 688 689In full-trace mode, the driver waits for data to be copied out before allowing 690the (logical) buffer to wrap-around. If data is not copied out quickly enough, 691again 'truncated' is set in the PERF_RECORD_AUX event. If the driver has to 692wait, the intel_pt event gets disabled. Because it is difficult to know when 693that happens, perf tools always re-enable the intel_pt event after copying out 694data. 695 696 697Intel PT and build ids 698~~~~~~~~~~~~~~~~~~~~~~ 699 700By default "perf record" post-processes the event stream to find all build ids 701for executables for all addresses sampled. Deliberately, Intel PT is not 702decoded for that purpose (it would take too long). Instead the build ids for 703all executables encountered (due to mmap, comm or task events) are included 704in the perf.data file. 705 706To see buildids included in the perf.data file use the command: 707 708 perf buildid-list 709 710If the perf.data file contains Intel PT data, that is the same as: 711 712 perf buildid-list --with-hits 713 714 715Snapshot mode and event disabling 716~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 717 718In order to make a snapshot, the intel_pt event is disabled using an IOCTL, 719namely PERF_EVENT_IOC_DISABLE. However doing that can also disable the 720collection of side-band information. In order to prevent that, a dummy 721software event has been introduced that permits tracking events (like mmaps) to 722continue to be recorded while intel_pt is disabled. That is important to ensure 723there is complete side-band information to allow the decoding of subsequent 724snapshots. 725 726A test has been created for that. To find the test: 727 728 perf test list 729 ... 730 23: Test using a dummy software event to keep tracking 731 732To run the test: 733 734 perf test 23 735 23: Test using a dummy software event to keep tracking : Ok 736 737 738perf record modes (nothing new here) 739~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 740 741perf record essentially operates in one of three modes: 742 per thread 743 per cpu 744 workload only 745 746"per thread" mode is selected by -t or by --per-thread (with -p or -u or just a 747workload). 748"per cpu" is selected by -C or -a. 749"workload only" mode is selected by not using the other options but providing a 750command to run (i.e. the workload). 751 752In per-thread mode an exact list of threads is traced. There is no inheritance. 753Each thread has its own event buffer. 754 755In per-cpu mode all processes (or processes from the selected cgroup i.e. -G 756option, or processes selected with -p or -u) are traced. Each cpu has its own 757buffer. Inheritance is allowed. 758 759In workload-only mode, the workload is traced but with per-cpu buffers. 760Inheritance is allowed. Note that you can now trace a workload in per-thread 761mode by using the --per-thread option. 762 763 764Privileged vs non-privileged users 765~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 766 767Unless /proc/sys/kernel/perf_event_paranoid is set to -1, unprivileged users 768have memory limits imposed upon them. That affects what buffer sizes they can 769have as outlined above. 770 771The v4.2 kernel introduced support for a context switch metadata event, 772PERF_RECORD_SWITCH, which allows unprivileged users to see when their processes 773are scheduled out and in, just not by whom, which is left for the 774PERF_RECORD_SWITCH_CPU_WIDE, that is only accessible in system wide context, 775which in turn requires CAP_PERFMON or CAP_SYS_ADMIN. 776 777Please see the 45ac1403f564 ("perf: Add PERF_RECORD_SWITCH to indicate context 778switches") commit, that introduces these metadata events for further info. 779 780When working with kernels < v4.2, the following considerations must be taken, 781as the sched:sched_switch tracepoints will be used to receive such information: 782 783Unless /proc/sys/kernel/perf_event_paranoid is set to -1, unprivileged users are 784not permitted to use tracepoints which means there is insufficient side-band 785information to decode Intel PT in per-cpu mode, and potentially workload-only 786mode too if the workload creates new processes. 787 788Note also, that to use tracepoints, read-access to debugfs is required. So if 789debugfs is not mounted or the user does not have read-access, it will again not 790be possible to decode Intel PT in per-cpu mode. 791 792 793sched_switch tracepoint 794~~~~~~~~~~~~~~~~~~~~~~~ 795 796The sched_switch tracepoint is used to provide side-band data for Intel PT 797decoding in kernels where the PERF_RECORD_SWITCH metadata event isn't 798available. 799 800The sched_switch events are automatically added. e.g. the second event shown 801below: 802 803 $ perf record -vv -e intel_pt//u uname 804 ------------------------------------------------------------ 805 perf_event_attr: 806 type 6 807 size 112 808 config 0x400 809 { sample_period, sample_freq } 1 810 sample_type IP|TID|TIME|CPU|IDENTIFIER 811 read_format ID 812 disabled 1 813 inherit 1 814 exclude_kernel 1 815 exclude_hv 1 816 enable_on_exec 1 817 sample_id_all 1 818 ------------------------------------------------------------ 819 sys_perf_event_open: pid 31104 cpu 0 group_fd -1 flags 0x8 820 sys_perf_event_open: pid 31104 cpu 1 group_fd -1 flags 0x8 821 sys_perf_event_open: pid 31104 cpu 2 group_fd -1 flags 0x8 822 sys_perf_event_open: pid 31104 cpu 3 group_fd -1 flags 0x8 823 ------------------------------------------------------------ 824 perf_event_attr: 825 type 2 826 size 112 827 config 0x108 828 { sample_period, sample_freq } 1 829 sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER 830 read_format ID 831 inherit 1 832 sample_id_all 1 833 exclude_guest 1 834 ------------------------------------------------------------ 835 sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 836 sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 837 sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8 838 sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8 839 ------------------------------------------------------------ 840 perf_event_attr: 841 type 1 842 size 112 843 config 0x9 844 { sample_period, sample_freq } 1 845 sample_type IP|TID|TIME|IDENTIFIER 846 read_format ID 847 disabled 1 848 inherit 1 849 exclude_kernel 1 850 exclude_hv 1 851 mmap 1 852 comm 1 853 enable_on_exec 1 854 task 1 855 sample_id_all 1 856 mmap2 1 857 comm_exec 1 858 ------------------------------------------------------------ 859 sys_perf_event_open: pid 31104 cpu 0 group_fd -1 flags 0x8 860 sys_perf_event_open: pid 31104 cpu 1 group_fd -1 flags 0x8 861 sys_perf_event_open: pid 31104 cpu 2 group_fd -1 flags 0x8 862 sys_perf_event_open: pid 31104 cpu 3 group_fd -1 flags 0x8 863 mmap size 528384B 864 AUX area mmap length 4194304 865 perf event ring buffer mmapped per cpu 866 Synthesizing auxtrace information 867 Linux 868 [ perf record: Woken up 1 times to write data ] 869 [ perf record: Captured and wrote 0.042 MB perf.data ] 870 871Note, the sched_switch event is only added if the user is permitted to use it 872and only in per-cpu mode. 873 874Note also, the sched_switch event is only added if TSC packets are requested. 875That is because, in the absence of timing information, the sched_switch events 876cannot be matched against the Intel PT trace. 877 878 879perf script 880----------- 881 882By default, perf script will decode trace data found in the perf.data file. 883This can be further controlled by new option --itrace. 884 885 886New --itrace option 887~~~~~~~~~~~~~~~~~~~ 888 889Having no option is the same as 890 891 --itrace 892 893which, in turn, is the same as 894 895 --itrace=cepwx 896 897The letters are: 898 899 i synthesize "instructions" events 900 b synthesize "branches" events 901 x synthesize "transactions" events 902 w synthesize "ptwrite" events 903 p synthesize "power" events (incl. PSB events) 904 c synthesize branches events (calls only) 905 r synthesize branches events (returns only) 906 o synthesize PEBS-via-PT events 907 I synthesize Event Trace events 908 e synthesize tracing error events 909 d create a debug log 910 g synthesize a call chain (use with i or x) 911 G synthesize a call chain on existing event records 912 l synthesize last branch entries (use with i or x) 913 L synthesize last branch entries on existing event records 914 s skip initial number of events 915 q quicker (less detailed) decoding 916 A approximate IPC 917 Z prefer to ignore timestamps (so-called "timeless" decoding) 918 919"Instructions" events look like they were recorded by "perf record -e 920instructions". 921 922"Branches" events look like they were recorded by "perf record -e branches". "c" 923and "r" can be combined to get calls and returns. 924 925"Transactions" events correspond to the start or end of transactions. The 926'flags' field can be used in perf script to determine whether the event is a 927transaction start, commit or abort. 928 929Note that "instructions", "branches" and "transactions" events depend on code 930flow packets which can be disabled by using the config term "branch=0". Refer 931to the config terms section above. 932 933"ptwrite" events record the payload of the ptwrite instruction and whether 934"fup_on_ptw" was used. "ptwrite" events depend on PTWRITE packets which are 935recorded only if the "ptw" config term was used. Refer to the config terms 936section above. perf script "synth" field displays "ptwrite" information like 937this: "ip: 0 payload: 0x123456789abcdef0" where "ip" is 1 if "fup_on_ptw" was 938used. 939 940"Power" events correspond to power event packets and CBR (core-to-bus ratio) 941packets. While CBR packets are always recorded when tracing is enabled, power 942event packets are recorded only if the "pwr_evt" config term was used. Refer to 943the config terms section above. The power events record information about 944C-state changes, whereas CBR is indicative of CPU frequency. perf script 945"event,synth" fields display information like this: 946 947 cbr: cbr: 22 freq: 2189 MHz (200%) 948 mwait: hints: 0x60 extensions: 0x1 949 pwre: hw: 0 cstate: 2 sub-cstate: 0 950 exstop: ip: 1 951 pwrx: deepest cstate: 2 last cstate: 2 wake reason: 0x4 952 953Where: 954 955 "cbr" includes the frequency and the percentage of maximum non-turbo 956 "mwait" shows mwait hints and extensions 957 "pwre" shows C-state transitions (to a C-state deeper than C0) and 958 whether initiated by hardware 959 "exstop" indicates execution stopped and whether the IP was recorded 960 exactly, 961 "pwrx" indicates return to C0 962 963For more details refer to the Intel 64 and IA-32 Architectures Software 964Developer Manuals. 965 966PSB events show when a PSB+ occurred and also the byte-offset in the trace. 967Emitting a PSB+ can cause a CPU a slight delay. When doing timing analysis 968of code with Intel PT, it is useful to know if a timing bubble was caused 969by Intel PT or not. 970 971Error events show where the decoder lost the trace. Error events 972are quite important. Users must know if what they are seeing is a complete 973picture or not. The "e" option may be followed by flags which affect what errors 974will or will not be reported. Each flag must be preceded by either '+' or '-'. 975The flags supported by Intel PT are: 976 977 -o Suppress overflow errors 978 -l Suppress trace data lost errors 979 980For example, for errors but not overflow or data lost errors: 981 982 --itrace=e-o-l 983 984The "d" option will cause the creation of a file "intel_pt.log" containing all 985decoded packets and instructions. Note that this option slows down the decoder 986and that the resulting file may be very large. The "d" option may be followed 987by flags which affect what debug messages will or will not be logged. Each flag 988must be preceded by either '+' or '-'. The flags support by Intel PT are: 989 990 -a Suppress logging of perf events 991 +a Log all perf events 992 +e Output only on decoding errors (size configurable) 993 +o Output to stdout instead of "intel_pt.log" 994 995By default, logged perf events are filtered by any specified time ranges, but 996flag +a overrides that. The +e flag can be useful for analyzing errors. By 997default, the log size in that case is 16384 bytes, but can be altered by 998linkperf:perf-config[1] e.g. perf config itrace.debug-log-buffer-size=30000 999 1000In addition, the period of the "instructions" event can be specified. e.g. 1001 1002 --itrace=i10us 1003 1004sets the period to 10us i.e. one instruction sample is synthesized for each 10 1005microseconds of trace. Alternatives to "us" are "ms" (milliseconds), 1006"ns" (nanoseconds), "t" (TSC ticks) or "i" (instructions). 1007 1008"ms", "us" and "ns" are converted to TSC ticks. 1009 1010The timing information included with Intel PT does not give the time of every 1011instruction. Consequently, for the purpose of sampling, the decoder estimates 1012the time since the last timing packet based on 1 tick per instruction. The time 1013on the sample is *not* adjusted and reflects the last known value of TSC. 1014 1015For Intel PT, the default period is 100us. 1016 1017Setting it to a zero period means "as often as possible". 1018 1019In the case of Intel PT that is the same as a period of 1 and a unit of 1020'instructions' (i.e. --itrace=i1i). 1021 1022Also the call chain size (default 16, max. 1024) for instructions or 1023transactions events can be specified. e.g. 1024 1025 --itrace=ig32 1026 --itrace=xg32 1027 1028Also the number of last branch entries (default 64, max. 1024) for instructions or 1029transactions events can be specified. e.g. 1030 1031 --itrace=il10 1032 --itrace=xl10 1033 1034Note that last branch entries are cleared for each sample, so there is no overlap 1035from one sample to the next. 1036 1037The G and L options are designed in particular for sample mode, and work much 1038like g and l but add call chain and branch stack to the other selected events 1039instead of synthesized events. For example, to record branch-misses events for 1040'ls' and then add a call chain derived from the Intel PT trace: 1041 1042 perf record --aux-sample -e '{intel_pt//u,branch-misses:u}' -- ls 1043 perf report --itrace=Ge 1044 1045Although in fact G is a default for perf report, so that is the same as just: 1046 1047 perf report 1048 1049One caveat with the G and L options is that they work poorly with "Large PEBS". 1050Large PEBS means PEBS records will be accumulated by hardware and the written 1051into the event buffer in one go. That reduces interrupts, but can give very 1052late timestamps. Because the Intel PT trace is synchronized by timestamps, 1053the PEBS events do not match the trace. Currently, Large PEBS is used only in 1054certain circumstances: 1055 - hardware supports it 1056 - PEBS is used 1057 - event period is specified, instead of frequency 1058 - the sample type is limited to the following flags: 1059 PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_ADDR | 1060 PERF_SAMPLE_ID | PERF_SAMPLE_CPU | PERF_SAMPLE_STREAM_ID | 1061 PERF_SAMPLE_DATA_SRC | PERF_SAMPLE_IDENTIFIER | 1062 PERF_SAMPLE_TRANSACTION | PERF_SAMPLE_PHYS_ADDR | 1063 PERF_SAMPLE_REGS_INTR | PERF_SAMPLE_REGS_USER | 1064 PERF_SAMPLE_PERIOD (and sometimes) | PERF_SAMPLE_TIME 1065Because Intel PT sample mode uses a different sample type to the list above, 1066Large PEBS is not used with Intel PT sample mode. To avoid Large PEBS in other 1067cases, avoid specifying the event period i.e. avoid the 'perf record' -c option, 1068--count option, or 'period' config term. 1069 1070To disable trace decoding entirely, use the option --no-itrace. 1071 1072It is also possible to skip events generated (instructions, branches, transactions) 1073at the beginning. This is useful to ignore initialization code. 1074 1075 --itrace=i0nss1000000 1076 1077skips the first million instructions. 1078 1079The q option changes the way the trace is decoded. The decoding is much faster 1080but much less detailed. Specifically, with the q option, the decoder does not 1081decode TNT packets, and does not walk object code, but gets the ip from FUP and 1082TIP packets. The q option can be used with the b and i options but the period 1083is not used. The q option decodes more quickly, but is useful only if the 1084control flow of interest is represented or indicated by FUP, TIP, TIP.PGE, or 1085TIP.PGD packets (refer below). However the q option could be used to find time 1086ranges that could then be decoded fully using the --time option. 1087 1088What will *not* be decoded with the (single) q option: 1089 1090 - direct calls and jmps 1091 - conditional branches 1092 - non-branch instructions 1093 1094What *will* be decoded with the (single) q option: 1095 1096 - asynchronous branches such as interrupts 1097 - indirect branches 1098 - function return target address *if* the noretcomp config term (refer 1099 config terms section) was used 1100 - start of (control-flow) tracing 1101 - end of (control-flow) tracing, if it is not out of context 1102 - power events, ptwrite, transaction start and abort 1103 - instruction pointer associated with PSB packets 1104 1105Note the q option does not specify what events will be synthesized e.g. the p 1106option must be used also to show power events. 1107 1108Repeating the q option (double-q i.e. qq) results in even faster decoding and even 1109less detail. The decoder decodes only extended PSB (PSB+) packets, getting the 1110instruction pointer if there is a FUP packet within PSB+ (i.e. between PSB and 1111PSBEND). Note PSB packets occur regularly in the trace based on the psb_period 1112config term (refer config terms section). There will be a FUP packet if the 1113PSB+ occurs while control flow is being traced. 1114 1115What will *not* be decoded with the qq option: 1116 1117 - everything except instruction pointer associated with PSB packets 1118 1119What *will* be decoded with the qq option: 1120 1121 - instruction pointer associated with PSB packets 1122 1123The Z option is equivalent to having recorded a trace without TSC 1124(i.e. config term tsc=0). It can be useful to avoid timestamp issues when 1125decoding a trace of a virtual machine. 1126 1127 1128dlfilter-show-cycles.so 1129~~~~~~~~~~~~~~~~~~~~~~~ 1130 1131Cycles can be displayed using dlfilter-show-cycles.so in which case the itrace A 1132option can be useful to provide higher granularity cycle information: 1133 1134 perf script --itrace=A --call-trace --dlfilter dlfilter-show-cycles.so 1135 1136To see a list of dlfilters: 1137 1138 perf script -v --list-dlfilters 1139 1140See also linkperf:perf-dlfilters[1] 1141 1142 1143dump option 1144~~~~~~~~~~~ 1145 1146perf script has an option (-D) to "dump" the events i.e. display the binary 1147data. 1148 1149When -D is used, Intel PT packets are displayed. The packet decoder does not 1150pay attention to PSB packets, but just decodes the bytes - so the packets seen 1151by the actual decoder may not be identical in places where the data is corrupt. 1152One example of that would be when the buffer-switching interrupt has been too 1153slow, and the buffer has been filled completely. In that case, the last packet 1154in the buffer might be truncated and immediately followed by a PSB as the trace 1155continues in the next buffer. 1156 1157To disable the display of Intel PT packets, combine the -D option with 1158--no-itrace. 1159 1160 1161perf report 1162----------- 1163 1164By default, perf report will decode trace data found in the perf.data file. 1165This can be further controlled by new option --itrace exactly the same as 1166perf script, with the exception that the default is --itrace=igxe. 1167 1168 1169perf inject 1170----------- 1171 1172perf inject also accepts the --itrace option in which case tracing data is 1173removed and replaced with the synthesized events. e.g. 1174 1175 perf inject --itrace -i perf.data -o perf.data.new 1176 1177Below is an example of using Intel PT with autofdo. It requires autofdo 1178(https://github.com/google/autofdo) and gcc version 5. The bubble 1179sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tutorial) 1180amended to take the number of elements as a parameter. 1181 1182 $ gcc-5 -O3 sort.c -o sort_optimized 1183 $ ./sort_optimized 30000 1184 Bubble sorting array of 30000 elements 1185 2254 ms 1186 1187 $ cat ~/.perfconfig 1188 [intel-pt] 1189 mispred-all = on 1190 1191 $ perf record -e intel_pt//u ./sort 3000 1192 Bubble sorting array of 3000 elements 1193 58 ms 1194 [ perf record: Woken up 2 times to write data ] 1195 [ perf record: Captured and wrote 3.939 MB perf.data ] 1196 $ perf inject -i perf.data -o inj --itrace=i100usle --strip 1197 $ ./create_gcov --binary=./sort --profile=inj --gcov=sort.gcov -gcov_version=1 1198 $ gcc-5 -O3 -fauto-profile=sort.gcov sort.c -o sort_autofdo 1199 $ ./sort_autofdo 30000 1200 Bubble sorting array of 30000 elements 1201 2155 ms 1202 1203Note there is currently no advantage to using Intel PT instead of LBR, but 1204that may change in the future if greater use is made of the data. 1205 1206 1207PEBS via Intel PT 1208----------------- 1209 1210Some hardware has the feature to redirect PEBS records to the Intel PT trace. 1211Recording is selected by using the aux-output config term e.g. 1212 1213 perf record -c 10000 -e '{intel_pt/branch=0/,cycles/aux-output/ppp}' uname 1214 1215Originally, software only supported redirecting at most one PEBS event because it 1216was not able to differentiate one event from another. To overcome that, more recent 1217kernels and perf tools add support for the PERF_RECORD_AUX_OUTPUT_HW_ID side-band event. 1218To check for the presence of that event in a PEBS-via-PT trace: 1219 1220 perf script -D --no-itrace | grep PERF_RECORD_AUX_OUTPUT_HW_ID 1221 1222To display PEBS events from the Intel PT trace, use the itrace 'o' option e.g. 1223 1224 perf script --itrace=oe 1225 1226XED 1227--- 1228 1229include::build-xed.txt[] 1230 1231 1232Tracing Virtual Machines (kernel only) 1233-------------------------------------- 1234 1235Currently, kernel tracing is supported with either "timeless" decoding 1236(i.e. no TSC timestamps) or VM Time Correlation. VM Time Correlation is an extra step 1237using 'perf inject' and requires unchanging VMX TSC Offset and no VMX TSC Scaling. 1238 1239Other limitations and caveats 1240 1241 VMX controls may suppress packets needed for decoding resulting in decoding errors 1242 VMX controls may block the perf NMI to the host potentially resulting in lost trace data 1243 Guest kernel self-modifying code (e.g. jump labels or JIT-compiled eBPF) will result in decoding errors 1244 Guest thread information is unknown 1245 Guest VCPU is unknown but may be able to be inferred from the host thread 1246 Callchains are not supported 1247 1248Example using "timeless" decoding 1249 1250Start VM 1251 1252 $ sudo virsh start kubuntu20.04 1253 Domain kubuntu20.04 started 1254 1255Mount the guest file system. Note sshfs needs -o direct_io to enable reading of proc files. root access is needed to read /proc/kcore. 1256 1257 $ mkdir vm0 1258 $ sshfs -o direct_io root@vm0:/ vm0 1259 1260Copy the guest /proc/kallsyms, /proc/modules and /proc/kcore 1261 1262 $ perf buildid-cache -v --kcore vm0/proc/kcore 1263 kcore added to build-id cache directory /home/user/.debug/[kernel.kcore]/9600f316a53a0f54278885e8d9710538ec5f6a08/2021021807494306 1264 $ KALLSYMS=/home/user/.debug/[kernel.kcore]/9600f316a53a0f54278885e8d9710538ec5f6a08/2021021807494306/kallsyms 1265 1266Find the VM process 1267 1268 $ ps -eLl | grep 'KVM\|PID' 1269 F S UID PID PPID LWP C PRI NI ADDR SZ WCHAN TTY TIME CMD 1270 3 S 64055 1430 1 1440 1 80 0 - 1921718 - ? 00:02:47 CPU 0/KVM 1271 3 S 64055 1430 1 1441 1 80 0 - 1921718 - ? 00:02:41 CPU 1/KVM 1272 3 S 64055 1430 1 1442 1 80 0 - 1921718 - ? 00:02:38 CPU 2/KVM 1273 3 S 64055 1430 1 1443 2 80 0 - 1921718 - ? 00:03:18 CPU 3/KVM 1274 1275Start an open-ended perf record, tracing the VM process, do something on the VM, and then ctrl-C to stop. 1276TSC is not supported and tsc=0 must be specified. That means mtc is useless, so add mtc=0. 1277However, IPC can still be determined, hence cyc=1 can be added. 1278Only kernel decoding is supported, so 'k' must be specified. 1279Intel PT traces both the host and the guest so --guest and --host need to be specified. 1280Without timestamps, --per-thread must be specified to distinguish threads. 1281 1282 $ sudo perf kvm --guest --host --guestkallsyms $KALLSYMS record --kcore -e intel_pt/tsc=0,mtc=0,cyc=1/k -p 1430 --per-thread 1283 ^C 1284 [ perf record: Woken up 1 times to write data ] 1285 [ perf record: Captured and wrote 5.829 MB ] 1286 1287perf script can be used to provide an instruction trace 1288 1289 $ perf script --guestkallsyms $KALLSYMS --insn-trace --xed -F+ipc | grep -C10 vmresume | head -21 1290 CPU 0/KVM 1440 ffffffff82133cdd __vmx_vcpu_run+0x3d ([kernel.kallsyms]) movq 0x48(%rax), %r9 1291 CPU 0/KVM 1440 ffffffff82133ce1 __vmx_vcpu_run+0x41 ([kernel.kallsyms]) movq 0x50(%rax), %r10 1292 CPU 0/KVM 1440 ffffffff82133ce5 __vmx_vcpu_run+0x45 ([kernel.kallsyms]) movq 0x58(%rax), %r11 1293 CPU 0/KVM 1440 ffffffff82133ce9 __vmx_vcpu_run+0x49 ([kernel.kallsyms]) movq 0x60(%rax), %r12 1294 CPU 0/KVM 1440 ffffffff82133ced __vmx_vcpu_run+0x4d ([kernel.kallsyms]) movq 0x68(%rax), %r13 1295 CPU 0/KVM 1440 ffffffff82133cf1 __vmx_vcpu_run+0x51 ([kernel.kallsyms]) movq 0x70(%rax), %r14 1296 CPU 0/KVM 1440 ffffffff82133cf5 __vmx_vcpu_run+0x55 ([kernel.kallsyms]) movq 0x78(%rax), %r15 1297 CPU 0/KVM 1440 ffffffff82133cf9 __vmx_vcpu_run+0x59 ([kernel.kallsyms]) movq (%rax), %rax 1298 CPU 0/KVM 1440 ffffffff82133cfc __vmx_vcpu_run+0x5c ([kernel.kallsyms]) callq 0xffffffff82133c40 1299 CPU 0/KVM 1440 ffffffff82133c40 vmx_vmenter+0x0 ([kernel.kallsyms]) jz 0xffffffff82133c46 1300 CPU 0/KVM 1440 ffffffff82133c42 vmx_vmenter+0x2 ([kernel.kallsyms]) vmresume IPC: 0.11 (50/445) 1301 :1440 1440 ffffffffbb678b06 native_write_msr+0x6 ([guest.kernel.kallsyms]) nopl %eax, (%rax,%rax,1) 1302 :1440 1440 ffffffffbb678b0b native_write_msr+0xb ([guest.kernel.kallsyms]) retq IPC: 0.04 (2/41) 1303 :1440 1440 ffffffffbb666646 lapic_next_deadline+0x26 ([guest.kernel.kallsyms]) data16 nop 1304 :1440 1440 ffffffffbb666648 lapic_next_deadline+0x28 ([guest.kernel.kallsyms]) xor %eax, %eax 1305 :1440 1440 ffffffffbb66664a lapic_next_deadline+0x2a ([guest.kernel.kallsyms]) popq %rbp 1306 :1440 1440 ffffffffbb66664b lapic_next_deadline+0x2b ([guest.kernel.kallsyms]) retq IPC: 0.16 (4/25) 1307 :1440 1440 ffffffffbb74607f clockevents_program_event+0x8f ([guest.kernel.kallsyms]) test %eax, %eax 1308 :1440 1440 ffffffffbb746081 clockevents_program_event+0x91 ([guest.kernel.kallsyms]) jz 0xffffffffbb74603c IPC: 0.06 (2/30) 1309 :1440 1440 ffffffffbb74603c clockevents_program_event+0x4c ([guest.kernel.kallsyms]) popq %rbx 1310 :1440 1440 ffffffffbb74603d clockevents_program_event+0x4d ([guest.kernel.kallsyms]) popq %r12 1311 1312Example using VM Time Correlation 1313 1314Start VM 1315 1316 $ sudo virsh start kubuntu20.04 1317 Domain kubuntu20.04 started 1318 1319Mount the guest file system. Note sshfs needs -o direct_io to enable reading of proc files. root access is needed to read /proc/kcore. 1320 1321 $ mkdir -p vm0 1322 $ sshfs -o direct_io root@vm0:/ vm0 1323 1324Copy the guest /proc/kallsyms, /proc/modules and /proc/kcore 1325 1326 $ perf buildid-cache -v --kcore vm0/proc/kcore 1327 same kcore found in /home/user/.debug/[kernel.kcore]/cc9c55a98c5e4ec0aeda69302554aabed5cd6491/2021021312450777 1328 $ KALLSYMS=/home/user/.debug/\[kernel.kcore\]/cc9c55a98c5e4ec0aeda69302554aabed5cd6491/2021021312450777/kallsyms 1329 1330Find the VM process 1331 1332 $ ps -eLl | grep 'KVM\|PID' 1333 F S UID PID PPID LWP C PRI NI ADDR SZ WCHAN TTY TIME CMD 1334 3 S 64055 16998 1 17005 13 80 0 - 1818189 - ? 00:00:16 CPU 0/KVM 1335 3 S 64055 16998 1 17006 4 80 0 - 1818189 - ? 00:00:05 CPU 1/KVM 1336 3 S 64055 16998 1 17007 3 80 0 - 1818189 - ? 00:00:04 CPU 2/KVM 1337 3 S 64055 16998 1 17008 4 80 0 - 1818189 - ? 00:00:05 CPU 3/KVM 1338 1339Start an open-ended perf record, tracing the VM process, do something on the VM, and then ctrl-C to stop. 1340IPC can be determined, hence cyc=1 can be added. 1341Only kernel decoding is supported, so 'k' must be specified. 1342Intel PT traces both the host and the guest so --guest and --host need to be specified. 1343 1344 $ sudo perf kvm --guest --host --guestkallsyms $KALLSYMS record --kcore -e intel_pt/cyc=1/k -p 16998 1345 ^C[ perf record: Woken up 1 times to write data ] 1346 [ perf record: Captured and wrote 9.041 MB perf.data.kvm ] 1347 1348Now 'perf inject' can be used to determine the VMX TCS Offset. Note, Intel PT TSC packets are 1349only 7-bytes, so the TSC Offset might differ from the actual value in the 8th byte. That will 1350have no effect i.e. the resulting timestamps will be correct anyway. 1351 1352 $ perf inject -i perf.data.kvm --vm-time-correlation=dry-run 1353 ERROR: Unknown TSC Offset for VMCS 0x1bff6a 1354 VMCS: 0x1bff6a TSC Offset 0xffffe42722c64c41 1355 ERROR: Unknown TSC Offset for VMCS 0x1cbc08 1356 VMCS: 0x1cbc08 TSC Offset 0xffffe42722c64c41 1357 ERROR: Unknown TSC Offset for VMCS 0x1c3ce8 1358 VMCS: 0x1c3ce8 TSC Offset 0xffffe42722c64c41 1359 ERROR: Unknown TSC Offset for VMCS 0x1cbce9 1360 VMCS: 0x1cbce9 TSC Offset 0xffffe42722c64c41 1361 1362Each virtual CPU has a different Virtual Machine Control Structure (VMCS) 1363shown above with the calculated TSC Offset. For an unchanging TSC Offset 1364they should all be the same for the same virtual machine. 1365 1366Now that the TSC Offset is known, it can be provided to 'perf inject' 1367 1368 $ perf inject -i perf.data.kvm --vm-time-correlation="dry-run 0xffffe42722c64c41" 1369 1370Note the options for 'perf inject' --vm-time-correlation are: 1371 1372 [ dry-run ] [ <TSC Offset> [ : <VMCS> [ , <VMCS> ]... ] ]... 1373 1374So it is possible to specify different TSC Offsets for different VMCS. 1375The option "dry-run" will cause the file to be processed but without updating it. 1376Note it is also possible to get a intel_pt.log file by adding option --itrace=d 1377 1378There were no errors so, do it for real 1379 1380 $ perf inject -i perf.data.kvm --vm-time-correlation=0xffffe42722c64c41 --force 1381 1382'perf script' can be used to see if there are any decoder errors 1383 1384 $ perf script -i perf.data.kvm --guestkallsyms $KALLSYMS --itrace=e-o 1385 1386There were none. 1387 1388'perf script' can be used to provide an instruction trace showing timestamps 1389 1390 $ perf script -i perf.data.kvm --guestkallsyms $KALLSYMS --insn-trace --xed -F+ipc | grep -C10 vmresume | head -21 1391 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133cdd __vmx_vcpu_run+0x3d ([kernel.kallsyms]) movq 0x48(%rax), %r9 1392 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133ce1 __vmx_vcpu_run+0x41 ([kernel.kallsyms]) movq 0x50(%rax), %r10 1393 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133ce5 __vmx_vcpu_run+0x45 ([kernel.kallsyms]) movq 0x58(%rax), %r11 1394 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133ce9 __vmx_vcpu_run+0x49 ([kernel.kallsyms]) movq 0x60(%rax), %r12 1395 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133ced __vmx_vcpu_run+0x4d ([kernel.kallsyms]) movq 0x68(%rax), %r13 1396 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133cf1 __vmx_vcpu_run+0x51 ([kernel.kallsyms]) movq 0x70(%rax), %r14 1397 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133cf5 __vmx_vcpu_run+0x55 ([kernel.kallsyms]) movq 0x78(%rax), %r15 1398 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133cf9 __vmx_vcpu_run+0x59 ([kernel.kallsyms]) movq (%rax), %rax 1399 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133cfc __vmx_vcpu_run+0x5c ([kernel.kallsyms]) callq 0xffffffff82133c40 1400 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133c40 vmx_vmenter+0x0 ([kernel.kallsyms]) jz 0xffffffff82133c46 1401 CPU 1/KVM 17006 [001] 11500.262866075: ffffffff82133c42 vmx_vmenter+0x2 ([kernel.kallsyms]) vmresume IPC: 0.05 (40/769) 1402 :17006 17006 [001] 11500.262869216: ffffffff82200cb0 asm_sysvec_apic_timer_interrupt+0x0 ([guest.kernel.kallsyms]) clac 1403 :17006 17006 [001] 11500.262869216: ffffffff82200cb3 asm_sysvec_apic_timer_interrupt+0x3 ([guest.kernel.kallsyms]) pushq $0xffffffffffffffff 1404 :17006 17006 [001] 11500.262869216: ffffffff82200cb5 asm_sysvec_apic_timer_interrupt+0x5 ([guest.kernel.kallsyms]) callq 0xffffffff82201160 1405 :17006 17006 [001] 11500.262869216: ffffffff82201160 error_entry+0x0 ([guest.kernel.kallsyms]) cld 1406 :17006 17006 [001] 11500.262869216: ffffffff82201161 error_entry+0x1 ([guest.kernel.kallsyms]) pushq %rsi 1407 :17006 17006 [001] 11500.262869216: ffffffff82201162 error_entry+0x2 ([guest.kernel.kallsyms]) movq 0x8(%rsp), %rsi 1408 :17006 17006 [001] 11500.262869216: ffffffff82201167 error_entry+0x7 ([guest.kernel.kallsyms]) movq %rdi, 0x8(%rsp) 1409 :17006 17006 [001] 11500.262869216: ffffffff8220116c error_entry+0xc ([guest.kernel.kallsyms]) pushq %rdx 1410 :17006 17006 [001] 11500.262869216: ffffffff8220116d error_entry+0xd ([guest.kernel.kallsyms]) pushq %rcx 1411 :17006 17006 [001] 11500.262869216: ffffffff8220116e error_entry+0xe ([guest.kernel.kallsyms]) pushq %rax 1412 1413 1414Tracing Virtual Machines (including user space) 1415----------------------------------------------- 1416 1417It is possible to use perf record to record sideband events within a virtual machine, so that an Intel PT trace on the host can be decoded. 1418Sideband events from the guest perf.data file can be injected into the host perf.data file using perf inject. 1419 1420Here is an example of the steps needed: 1421 1422On the guest machine: 1423 1424Check that no-kvmclock kernel command line option was used to boot: 1425 1426Note, this is essential to enable time correlation between host and guest machines. 1427 1428 $ cat /proc/cmdline 1429 BOOT_IMAGE=/boot/vmlinuz-5.10.0-16-amd64 root=UUID=cb49c910-e573-47e0-bce7-79e293df8e1d ro no-kvmclock 1430 1431There is no BPF support at present so, if possible, disable JIT compiling: 1432 1433 $ echo 0 | sudo tee /proc/sys/net/core/bpf_jit_enable 1434 0 1435 1436Start perf record to collect sideband events: 1437 1438 $ sudo perf record -o guest-sideband-testing-guest-perf.data --sample-identifier --buildid-all --switch-events --kcore -a -e dummy 1439 1440On the host machine: 1441 1442Start perf record to collect Intel PT trace: 1443 1444Note, the host trace will get very big, very fast, so the steps from starting to stopping the host trace really need to be done so that they happen in the shortest time possible. 1445 1446 $ sudo perf record -o guest-sideband-testing-host-perf.data -m,64M --kcore -a -e intel_pt/cyc/ 1447 1448On the guest machine: 1449 1450Run a small test case, just 'uname' in this example: 1451 1452 $ uname 1453 Linux 1454 1455On the host machine: 1456 1457Stop the Intel PT trace: 1458 1459 ^C 1460 [ perf record: Woken up 1 times to write data ] 1461 [ perf record: Captured and wrote 76.122 MB guest-sideband-testing-host-perf.data ] 1462 1463On the guest machine: 1464 1465Stop the Intel PT trace: 1466 1467 ^C 1468 [ perf record: Woken up 1 times to write data ] 1469 [ perf record: Captured and wrote 1.247 MB guest-sideband-testing-guest-perf.data ] 1470 1471And then copy guest-sideband-testing-guest-perf.data to the host (not shown here). 1472 1473On the host machine: 1474 1475With the 2 perf.data recordings, and with their ownership changed to the user. 1476 1477Identify the TSC Offset: 1478 1479 $ perf inject -i guest-sideband-testing-host-perf.data --vm-time-correlation=dry-run 1480 VMCS: 0x103fc6 TSC Offset 0xfffffa6ae070cb20 1481 VMCS: 0x103ff2 TSC Offset 0xfffffa6ae070cb20 1482 VMCS: 0x10fdaa TSC Offset 0xfffffa6ae070cb20 1483 VMCS: 0x24d57c TSC Offset 0xfffffa6ae070cb20 1484 1485Correct Intel PT TSC timestamps for the guest machine: 1486 1487 $ perf inject -i guest-sideband-testing-host-perf.data --vm-time-correlation=0xfffffa6ae070cb20 --force 1488 1489Identify the guest machine PID: 1490 1491 $ perf script -i guest-sideband-testing-host-perf.data --no-itrace --show-task-events | grep KVM 1492 CPU 0/KVM 0 [000] 0.000000: PERF_RECORD_COMM: CPU 0/KVM:13376/13381 1493 CPU 1/KVM 0 [000] 0.000000: PERF_RECORD_COMM: CPU 1/KVM:13376/13382 1494 CPU 2/KVM 0 [000] 0.000000: PERF_RECORD_COMM: CPU 2/KVM:13376/13383 1495 CPU 3/KVM 0 [000] 0.000000: PERF_RECORD_COMM: CPU 3/KVM:13376/13384 1496 1497Note, the QEMU option -name debug-threads=on is needed so that thread names 1498can be used to determine which thread is running which VCPU as above. libvirt seems to use this by default. 1499 1500Create a guestmount, assuming the guest machine is 'vm_to_test': 1501 1502 $ mkdir -p ~/guestmount/13376 1503 $ sshfs -o direct_io vm_to_test:/ ~/guestmount/13376 1504 1505Inject the guest perf.data file into the host perf.data file: 1506 1507Note, due to the guestmount option, guest object files and debug files will be copied into the build ID cache from the guest machine, with the notable exception of VDSO. 1508If needed, VDSO can be copied manually in a fashion similar to that used by the perf-archive script. 1509 1510 $ perf inject -i guest-sideband-testing-host-perf.data -o inj --guestmount ~/guestmount --guest-data=guest-sideband-testing-guest-perf.data,13376,0xfffffa6ae070cb20 1511 1512Show an excerpt from the result. In this case the CPU and time range have been to chosen to show interaction between guest and host when 'uname' is starting to run on the guest machine: 1513 1514Notes: 1515 1516 - the CPU displayed, [002] in this case, is always the host CPU 1517 - events happening in the virtual machine start with VM:13376 VCPU:003, which shows the hypervisor PID 13376 and the VCPU number 1518 - only calls and errors are displayed i.e. --itrace=ce 1519 - branches entering and exiting the virtual machine are split, and show as 2 branches to/from "0 [unknown] ([unknown])" 1520 1521 $ perf script -i inj --itrace=ce -F+machine_pid,+vcpu,+addr,+pid,+tid,-period --ns --time 7919.408803365,7919.408804631 -C 2 1522 CPU 3/KVM 13376/13384 [002] 7919.408803365: branches: ffffffffc0f8ebe0 vmx_vcpu_enter_exit+0xc0 ([kernel.kallsyms]) => ffffffffc0f8edc0 __vmx_vcpu_run+0x0 ([kernel.kallsyms]) 1523 CPU 3/KVM 13376/13384 [002] 7919.408803365: branches: ffffffffc0f8edd5 __vmx_vcpu_run+0x15 ([kernel.kallsyms]) => ffffffffc0f8eca0 vmx_update_host_rsp+0x0 ([kernel.kallsyms]) 1524 CPU 3/KVM 13376/13384 [002] 7919.408803365: branches: ffffffffc0f8ee1b __vmx_vcpu_run+0x5b ([kernel.kallsyms]) => ffffffffc0f8ed60 vmx_vmenter+0x0 ([kernel.kallsyms]) 1525 CPU 3/KVM 13376/13384 [002] 7919.408803461: branches: ffffffffc0f8ed62 vmx_vmenter+0x2 ([kernel.kallsyms]) => 0 [unknown] ([unknown]) 1526 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408803461: branches: 0 [unknown] ([unknown]) => 7f851c9b5a5c init_cacheinfo+0x3ac (/usr/lib/x86_64-linux-gnu/libc-2.31.so) 1527 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408803567: branches: 7f851c9b5a5a init_cacheinfo+0x3aa (/usr/lib/x86_64-linux-gnu/libc-2.31.so) => 0 [unknown] ([unknown]) 1528 CPU 3/KVM 13376/13384 [002] 7919.408803567: branches: 0 [unknown] ([unknown]) => ffffffffc0f8ed80 vmx_vmexit+0x0 ([kernel.kallsyms]) 1529 CPU 3/KVM 13376/13384 [002] 7919.408803596: branches: ffffffffc0f6619a vmx_vcpu_run+0x26a ([kernel.kallsyms]) => ffffffffb2255c60 x86_virt_spec_ctrl+0x0 ([kernel.kallsyms]) 1530 CPU 3/KVM 13376/13384 [002] 7919.408803801: branches: ffffffffc0f66445 vmx_vcpu_run+0x515 ([kernel.kallsyms]) => ffffffffb2290b30 native_write_msr+0x0 ([kernel.kallsyms]) 1531 CPU 3/KVM 13376/13384 [002] 7919.408803850: branches: ffffffffc0f661f8 vmx_vcpu_run+0x2c8 ([kernel.kallsyms]) => ffffffffc1092300 kvm_load_host_xsave_state+0x0 ([kernel.kallsyms]) 1532 CPU 3/KVM 13376/13384 [002] 7919.408803850: branches: ffffffffc1092327 kvm_load_host_xsave_state+0x27 ([kernel.kallsyms]) => ffffffffc1092220 kvm_load_host_xsave_state.part.0+0x0 ([kernel.kallsyms]) 1533 CPU 3/KVM 13376/13384 [002] 7919.408803862: branches: ffffffffc0f662cf vmx_vcpu_run+0x39f ([kernel.kallsyms]) => ffffffffc0f63f90 vmx_recover_nmi_blocking+0x0 ([kernel.kallsyms]) 1534 CPU 3/KVM 13376/13384 [002] 7919.408803862: branches: ffffffffc0f662e9 vmx_vcpu_run+0x3b9 ([kernel.kallsyms]) => ffffffffc0f619a0 __vmx_complete_interrupts+0x0 ([kernel.kallsyms]) 1535 CPU 3/KVM 13376/13384 [002] 7919.408803872: branches: ffffffffc109cfb2 vcpu_enter_guest+0x752 ([kernel.kallsyms]) => ffffffffc0f5f570 vmx_handle_exit_irqoff+0x0 ([kernel.kallsyms]) 1536 CPU 3/KVM 13376/13384 [002] 7919.408803881: branches: ffffffffc109d028 vcpu_enter_guest+0x7c8 ([kernel.kallsyms]) => ffffffffb234f900 __srcu_read_lock+0x0 ([kernel.kallsyms]) 1537 CPU 3/KVM 13376/13384 [002] 7919.408803897: branches: ffffffffc109d06f vcpu_enter_guest+0x80f ([kernel.kallsyms]) => ffffffffc0f72e30 vmx_handle_exit+0x0 ([kernel.kallsyms]) 1538 CPU 3/KVM 13376/13384 [002] 7919.408803897: branches: ffffffffc0f72e3d vmx_handle_exit+0xd ([kernel.kallsyms]) => ffffffffc0f727c0 __vmx_handle_exit+0x0 ([kernel.kallsyms]) 1539 CPU 3/KVM 13376/13384 [002] 7919.408803897: branches: ffffffffc0f72b15 __vmx_handle_exit+0x355 ([kernel.kallsyms]) => ffffffffc0f60ae0 vmx_flush_pml_buffer+0x0 ([kernel.kallsyms]) 1540 CPU 3/KVM 13376/13384 [002] 7919.408803903: branches: ffffffffc0f72994 __vmx_handle_exit+0x1d4 ([kernel.kallsyms]) => ffffffffc10b7090 kvm_emulate_cpuid+0x0 ([kernel.kallsyms]) 1541 CPU 3/KVM 13376/13384 [002] 7919.408803903: branches: ffffffffc10b70f1 kvm_emulate_cpuid+0x61 ([kernel.kallsyms]) => ffffffffc10b6e10 kvm_cpuid+0x0 ([kernel.kallsyms]) 1542 CPU 3/KVM 13376/13384 [002] 7919.408803941: branches: ffffffffc10b7125 kvm_emulate_cpuid+0x95 ([kernel.kallsyms]) => ffffffffc1093110 kvm_skip_emulated_instruction+0x0 ([kernel.kallsyms]) 1543 CPU 3/KVM 13376/13384 [002] 7919.408803941: branches: ffffffffc109311f kvm_skip_emulated_instruction+0xf ([kernel.kallsyms]) => ffffffffc0f5e180 vmx_get_rflags+0x0 ([kernel.kallsyms]) 1544 CPU 3/KVM 13376/13384 [002] 7919.408803951: branches: ffffffffc109312a kvm_skip_emulated_instruction+0x1a ([kernel.kallsyms]) => ffffffffc0f5fd30 vmx_skip_emulated_instruction+0x0 ([kernel.kallsyms]) 1545 CPU 3/KVM 13376/13384 [002] 7919.408803951: branches: ffffffffc0f5fd79 vmx_skip_emulated_instruction+0x49 ([kernel.kallsyms]) => ffffffffc0f5fb50 skip_emulated_instruction+0x0 ([kernel.kallsyms]) 1546 CPU 3/KVM 13376/13384 [002] 7919.408803956: branches: ffffffffc0f5fc68 skip_emulated_instruction+0x118 ([kernel.kallsyms]) => ffffffffc0f6a940 vmx_cache_reg+0x0 ([kernel.kallsyms]) 1547 CPU 3/KVM 13376/13384 [002] 7919.408803964: branches: ffffffffc0f5fc11 skip_emulated_instruction+0xc1 ([kernel.kallsyms]) => ffffffffc0f5f9e0 vmx_set_interrupt_shadow+0x0 ([kernel.kallsyms]) 1548 CPU 3/KVM 13376/13384 [002] 7919.408803980: branches: ffffffffc109f8b1 vcpu_run+0x71 ([kernel.kallsyms]) => ffffffffc10ad2f0 kvm_cpu_has_pending_timer+0x0 ([kernel.kallsyms]) 1549 CPU 3/KVM 13376/13384 [002] 7919.408803980: branches: ffffffffc10ad2fb kvm_cpu_has_pending_timer+0xb ([kernel.kallsyms]) => ffffffffc10b0490 apic_has_pending_timer+0x0 ([kernel.kallsyms]) 1550 CPU 3/KVM 13376/13384 [002] 7919.408803991: branches: ffffffffc109f899 vcpu_run+0x59 ([kernel.kallsyms]) => ffffffffc109c860 vcpu_enter_guest+0x0 ([kernel.kallsyms]) 1551 CPU 3/KVM 13376/13384 [002] 7919.408803993: branches: ffffffffc109cd4c vcpu_enter_guest+0x4ec ([kernel.kallsyms]) => ffffffffc0f69140 vmx_prepare_switch_to_guest+0x0 ([kernel.kallsyms]) 1552 CPU 3/KVM 13376/13384 [002] 7919.408803996: branches: ffffffffc109cd7d vcpu_enter_guest+0x51d ([kernel.kallsyms]) => ffffffffb234f930 __srcu_read_unlock+0x0 ([kernel.kallsyms]) 1553 CPU 3/KVM 13376/13384 [002] 7919.408803996: branches: ffffffffc109cd9c vcpu_enter_guest+0x53c ([kernel.kallsyms]) => ffffffffc0f609b0 vmx_sync_pir_to_irr+0x0 ([kernel.kallsyms]) 1554 CPU 3/KVM 13376/13384 [002] 7919.408803996: branches: ffffffffc0f60a6d vmx_sync_pir_to_irr+0xbd ([kernel.kallsyms]) => ffffffffc10adc20 kvm_lapic_find_highest_irr+0x0 ([kernel.kallsyms]) 1555 CPU 3/KVM 13376/13384 [002] 7919.408804010: branches: ffffffffc0f60abd vmx_sync_pir_to_irr+0x10d ([kernel.kallsyms]) => ffffffffc0f60820 vmx_set_rvi+0x0 ([kernel.kallsyms]) 1556 CPU 3/KVM 13376/13384 [002] 7919.408804019: branches: ffffffffc109ceca vcpu_enter_guest+0x66a ([kernel.kallsyms]) => ffffffffb2249840 fpregs_assert_state_consistent+0x0 ([kernel.kallsyms]) 1557 CPU 3/KVM 13376/13384 [002] 7919.408804021: branches: ffffffffc109cf10 vcpu_enter_guest+0x6b0 ([kernel.kallsyms]) => ffffffffc0f65f30 vmx_vcpu_run+0x0 ([kernel.kallsyms]) 1558 CPU 3/KVM 13376/13384 [002] 7919.408804024: branches: ffffffffc0f6603b vmx_vcpu_run+0x10b ([kernel.kallsyms]) => ffffffffb229bed0 __get_current_cr3_fast+0x0 ([kernel.kallsyms]) 1559 CPU 3/KVM 13376/13384 [002] 7919.408804024: branches: ffffffffc0f66055 vmx_vcpu_run+0x125 ([kernel.kallsyms]) => ffffffffb2253050 cr4_read_shadow+0x0 ([kernel.kallsyms]) 1560 CPU 3/KVM 13376/13384 [002] 7919.408804030: branches: ffffffffc0f6608d vmx_vcpu_run+0x15d ([kernel.kallsyms]) => ffffffffc10921e0 kvm_load_guest_xsave_state+0x0 ([kernel.kallsyms]) 1561 CPU 3/KVM 13376/13384 [002] 7919.408804030: branches: ffffffffc1092207 kvm_load_guest_xsave_state+0x27 ([kernel.kallsyms]) => ffffffffc1092110 kvm_load_guest_xsave_state.part.0+0x0 ([kernel.kallsyms]) 1562 CPU 3/KVM 13376/13384 [002] 7919.408804032: branches: ffffffffc0f660c6 vmx_vcpu_run+0x196 ([kernel.kallsyms]) => ffffffffb22061a0 perf_guest_get_msrs+0x0 ([kernel.kallsyms]) 1563 CPU 3/KVM 13376/13384 [002] 7919.408804032: branches: ffffffffb22061a9 perf_guest_get_msrs+0x9 ([kernel.kallsyms]) => ffffffffb220cda0 intel_guest_get_msrs+0x0 ([kernel.kallsyms]) 1564 CPU 3/KVM 13376/13384 [002] 7919.408804039: branches: ffffffffc0f66109 vmx_vcpu_run+0x1d9 ([kernel.kallsyms]) => ffffffffc0f652c0 clear_atomic_switch_msr+0x0 ([kernel.kallsyms]) 1565 CPU 3/KVM 13376/13384 [002] 7919.408804040: branches: ffffffffc0f66119 vmx_vcpu_run+0x1e9 ([kernel.kallsyms]) => ffffffffc0f73f60 intel_pmu_lbr_is_enabled+0x0 ([kernel.kallsyms]) 1566 CPU 3/KVM 13376/13384 [002] 7919.408804042: branches: ffffffffc0f73f81 intel_pmu_lbr_is_enabled+0x21 ([kernel.kallsyms]) => ffffffffc10b68e0 kvm_find_cpuid_entry+0x0 ([kernel.kallsyms]) 1567 CPU 3/KVM 13376/13384 [002] 7919.408804045: branches: ffffffffc0f66454 vmx_vcpu_run+0x524 ([kernel.kallsyms]) => ffffffffc0f61ff0 vmx_update_hv_timer+0x0 ([kernel.kallsyms]) 1568 CPU 3/KVM 13376/13384 [002] 7919.408804057: branches: ffffffffc0f66142 vmx_vcpu_run+0x212 ([kernel.kallsyms]) => ffffffffc10af100 kvm_wait_lapic_expire+0x0 ([kernel.kallsyms]) 1569 CPU 3/KVM 13376/13384 [002] 7919.408804057: branches: ffffffffc0f66156 vmx_vcpu_run+0x226 ([kernel.kallsyms]) => ffffffffb2255c60 x86_virt_spec_ctrl+0x0 ([kernel.kallsyms]) 1570 CPU 3/KVM 13376/13384 [002] 7919.408804057: branches: ffffffffc0f66161 vmx_vcpu_run+0x231 ([kernel.kallsyms]) => ffffffffc0f8eb20 vmx_vcpu_enter_exit+0x0 ([kernel.kallsyms]) 1571 CPU 3/KVM 13376/13384 [002] 7919.408804057: branches: ffffffffc0f8eb44 vmx_vcpu_enter_exit+0x24 ([kernel.kallsyms]) => ffffffffb2353e10 rcu_note_context_switch+0x0 ([kernel.kallsyms]) 1572 CPU 3/KVM 13376/13384 [002] 7919.408804057: branches: ffffffffb2353e1c rcu_note_context_switch+0xc ([kernel.kallsyms]) => ffffffffb2353db0 rcu_qs+0x0 ([kernel.kallsyms]) 1573 CPU 3/KVM 13376/13384 [002] 7919.408804066: branches: ffffffffc0f8ebe0 vmx_vcpu_enter_exit+0xc0 ([kernel.kallsyms]) => ffffffffc0f8edc0 __vmx_vcpu_run+0x0 ([kernel.kallsyms]) 1574 CPU 3/KVM 13376/13384 [002] 7919.408804066: branches: ffffffffc0f8edd5 __vmx_vcpu_run+0x15 ([kernel.kallsyms]) => ffffffffc0f8eca0 vmx_update_host_rsp+0x0 ([kernel.kallsyms]) 1575 CPU 3/KVM 13376/13384 [002] 7919.408804066: branches: ffffffffc0f8ee1b __vmx_vcpu_run+0x5b ([kernel.kallsyms]) => ffffffffc0f8ed60 vmx_vmenter+0x0 ([kernel.kallsyms]) 1576 CPU 3/KVM 13376/13384 [002] 7919.408804162: branches: ffffffffc0f8ed62 vmx_vmenter+0x2 ([kernel.kallsyms]) => 0 [unknown] ([unknown]) 1577 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804162: branches: 0 [unknown] ([unknown]) => 7f851c9b5a5c init_cacheinfo+0x3ac (/usr/lib/x86_64-linux-gnu/libc-2.31.so) 1578 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804273: branches: 7f851cb7c0e4 _dl_init+0x74 (/usr/lib/x86_64-linux-gnu/ld-2.31.so) => 7f851cb7bf50 call_init.part.0+0x0 (/usr/lib/x86_64-linux-gnu/ld-2.31.so) 1579 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804526: branches: 55e0c00136f0 _start+0x0 (/usr/bin/uname) => ffffffff83200ac0 asm_exc_page_fault+0x0 ([kernel.kallsyms]) 1580 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804526: branches: ffffffff83200ac3 asm_exc_page_fault+0x3 ([kernel.kallsyms]) => ffffffff83201290 error_entry+0x0 ([kernel.kallsyms]) 1581 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804534: branches: ffffffff832012fa error_entry+0x6a ([kernel.kallsyms]) => ffffffff830b59a0 sync_regs+0x0 ([kernel.kallsyms]) 1582 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804631: branches: ffffffff83200ad9 asm_exc_page_fault+0x19 ([kernel.kallsyms]) => ffffffff830b8210 exc_page_fault+0x0 ([kernel.kallsyms]) 1583 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804631: branches: ffffffff830b82a4 exc_page_fault+0x94 ([kernel.kallsyms]) => ffffffff830b80e0 __kvm_handle_async_pf+0x0 ([kernel.kallsyms]) 1584 VM:13376 VCPU:003 uname 3404/3404 [002] 7919.408804631: branches: ffffffff830b80ed __kvm_handle_async_pf+0xd ([kernel.kallsyms]) => ffffffff830b80c0 kvm_read_and_reset_apf_flags+0x0 ([kernel.kallsyms]) 1585 1586 1587Tracing Virtual Machines - Guest Code 1588------------------------------------- 1589 1590A common case for KVM test programs is that the test program acts as the 1591hypervisor, creating, running and destroying the virtual machine, and 1592providing the guest object code from its own object code. In this case, 1593the VM is not running an OS, but only the functions loaded into it by the 1594hypervisor test program, and conveniently, loaded at the same virtual 1595addresses. To support that, option "--guest-code" has been added to perf script 1596and perf kvm report. 1597 1598Here is an example tracing a test program from the kernel's KVM selftests: 1599 1600 # perf record --kcore -e intel_pt/cyc/ -- tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test 1601 [ perf record: Woken up 1 times to write data ] 1602 [ perf record: Captured and wrote 0.280 MB perf.data ] 1603 # perf script --guest-code --itrace=bep --ns -F-period,+addr,+flags 1604 [SNIP] 1605 tsc_msrs_test 18436 [007] 10897.962087733: branches: call ffffffffc13b2ff5 __vmx_vcpu_run+0x15 (vmlinux) => ffffffffc13b2f50 vmx_update_host_rsp+0x0 (vmlinux) 1606 tsc_msrs_test 18436 [007] 10897.962087733: branches: return ffffffffc13b2f5d vmx_update_host_rsp+0xd (vmlinux) => ffffffffc13b2ffa __vmx_vcpu_run+0x1a (vmlinux) 1607 tsc_msrs_test 18436 [007] 10897.962087733: branches: call ffffffffc13b303b __vmx_vcpu_run+0x5b (vmlinux) => ffffffffc13b2f80 vmx_vmenter+0x0 (vmlinux) 1608 tsc_msrs_test 18436 [007] 10897.962087836: branches: vmentry ffffffffc13b2f82 vmx_vmenter+0x2 (vmlinux) => 0 [unknown] ([unknown]) 1609 [guest/18436] 18436 [007] 10897.962087836: branches: vmentry 0 [unknown] ([unknown]) => 402c81 guest_code+0x131 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) 1610 [guest/18436] 18436 [007] 10897.962087836: branches: call 402c81 guest_code+0x131 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) => 40dba0 ucall+0x0 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) 1611 [guest/18436] 18436 [007] 10897.962088248: branches: vmexit 40dba0 ucall+0x0 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) => 0 [unknown] ([unknown]) 1612 tsc_msrs_test 18436 [007] 10897.962088248: branches: vmexit 0 [unknown] ([unknown]) => ffffffffc13b2fa0 vmx_vmexit+0x0 (vmlinux) 1613 tsc_msrs_test 18436 [007] 10897.962088248: branches: jmp ffffffffc13b2fa0 vmx_vmexit+0x0 (vmlinux) => ffffffffc13b2fd2 vmx_vmexit+0x32 (vmlinux) 1614 tsc_msrs_test 18436 [007] 10897.962088256: branches: return ffffffffc13b2fd2 vmx_vmexit+0x32 (vmlinux) => ffffffffc13b3040 __vmx_vcpu_run+0x60 (vmlinux) 1615 tsc_msrs_test 18436 [007] 10897.962088270: branches: return ffffffffc13b30b6 __vmx_vcpu_run+0xd6 (vmlinux) => ffffffffc13b2f2e vmx_vcpu_enter_exit+0x4e (vmlinux) 1616 [SNIP] 1617 tsc_msrs_test 18436 [007] 10897.962089321: branches: call ffffffffc13b2ff5 __vmx_vcpu_run+0x15 (vmlinux) => ffffffffc13b2f50 vmx_update_host_rsp+0x0 (vmlinux) 1618 tsc_msrs_test 18436 [007] 10897.962089321: branches: return ffffffffc13b2f5d vmx_update_host_rsp+0xd (vmlinux) => ffffffffc13b2ffa __vmx_vcpu_run+0x1a (vmlinux) 1619 tsc_msrs_test 18436 [007] 10897.962089321: branches: call ffffffffc13b303b __vmx_vcpu_run+0x5b (vmlinux) => ffffffffc13b2f80 vmx_vmenter+0x0 (vmlinux) 1620 tsc_msrs_test 18436 [007] 10897.962089424: branches: vmentry ffffffffc13b2f82 vmx_vmenter+0x2 (vmlinux) => 0 [unknown] ([unknown]) 1621 [guest/18436] 18436 [007] 10897.962089424: branches: vmentry 0 [unknown] ([unknown]) => 40dba0 ucall+0x0 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) 1622 [guest/18436] 18436 [007] 10897.962089701: branches: jmp 40dc1b ucall+0x7b (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) => 40dc39 ucall+0x99 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) 1623 [guest/18436] 18436 [007] 10897.962089701: branches: jcc 40dc3c ucall+0x9c (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) => 40dc20 ucall+0x80 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) 1624 [guest/18436] 18436 [007] 10897.962089701: branches: jcc 40dc3c ucall+0x9c (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) => 40dc20 ucall+0x80 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) 1625 [guest/18436] 18436 [007] 10897.962089701: branches: jcc 40dc37 ucall+0x97 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) => 40dc50 ucall+0xb0 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) 1626 [guest/18436] 18436 [007] 10897.962089878: branches: vmexit 40dc55 ucall+0xb5 (/home/user/git/work/tools/testing/selftests/kselftest_install/kvm/tsc_msrs_test) => 0 [unknown] ([unknown]) 1627 tsc_msrs_test 18436 [007] 10897.962089878: branches: vmexit 0 [unknown] ([unknown]) => ffffffffc13b2fa0 vmx_vmexit+0x0 (vmlinux) 1628 tsc_msrs_test 18436 [007] 10897.962089878: branches: jmp ffffffffc13b2fa0 vmx_vmexit+0x0 (vmlinux) => ffffffffc13b2fd2 vmx_vmexit+0x32 (vmlinux) 1629 tsc_msrs_test 18436 [007] 10897.962089887: branches: return ffffffffc13b2fd2 vmx_vmexit+0x32 (vmlinux) => ffffffffc13b3040 __vmx_vcpu_run+0x60 (vmlinux) 1630 tsc_msrs_test 18436 [007] 10897.962089901: branches: return ffffffffc13b30b6 __vmx_vcpu_run+0xd6 (vmlinux) => ffffffffc13b2f2e vmx_vcpu_enter_exit+0x4e (vmlinux) 1631 [SNIP] 1632 1633 # perf kvm --guest-code --guest --host report -i perf.data --stdio | head -20 1634 1635 # To display the perf.data header info, please use --header/--header-only options. 1636 # 1637 # 1638 # Total Lost Samples: 0 1639 # 1640 # Samples: 12 of event 'instructions' 1641 # Event count (approx.): 2274583 1642 # 1643 # Children Self Command Shared Object Symbol 1644 # ........ ........ ............. .................... ........................................... 1645 # 1646 54.70% 0.00% tsc_msrs_test [kernel.vmlinux] [k] entry_SYSCALL_64_after_hwframe 1647 | 1648 ---entry_SYSCALL_64_after_hwframe 1649 do_syscall_64 1650 | 1651 |--29.44%--syscall_exit_to_user_mode 1652 | exit_to_user_mode_prepare 1653 | task_work_run 1654 | __fput 1655 1656 1657Event Trace 1658----------- 1659 1660Event Trace records information about asynchronous events, for example interrupts, 1661faults, VM exits and entries. The information is recorded in CFE and EVD packets, 1662and also the Interrupt Flag is recorded on the MODE.Exec packet. The CFE packet 1663contains a type field to identify one of the following: 1664 1665 1 INTR interrupt, fault, exception, NMI 1666 2 IRET interrupt return 1667 3 SMI system management interrupt 1668 4 RSM resume from system management mode 1669 5 SIPI startup interprocessor interrupt 1670 6 INIT INIT signal 1671 7 VMENTRY VM-Entry 1672 8 VMEXIT VM-Entry 1673 9 VMEXIT_INTR VM-Exit due to interrupt 1674 10 SHUTDOWN Shutdown 1675 1676For more details, refer to the Intel 64 and IA-32 Architectures Software 1677Developer Manuals (version 076 or later). 1678 1679The capability to do Event Trace is indicated by the 1680/sys/bus/event_source/devices/intel_pt/caps/event_trace file. 1681 1682Event trace is selected for recording using the "event" config term. e.g. 1683 1684 perf record -e intel_pt/event/u uname 1685 1686Event trace events are output using the --itrace I option. e.g. 1687 1688 perf script --itrace=Ie 1689 1690perf script displays events containing CFE type, vector and event data, 1691in the form: 1692 1693 evt: hw int (t) cfe: INTR IP: 1 vector: 3 PFA: 0x8877665544332211 1694 1695The IP flag indicates if the event binds to an IP, which includes any case where 1696flow control packet generation is enabled, as well as when CFE packet IP bit is 1697set. 1698 1699perf script displays events containing changes to the Interrupt Flag in the form: 1700 1701 iflag: t IFLAG: 1->0 via branch 1702 1703where "via branch" indicates a branch (interrupt or return from interrupt) and 1704"non branch" indicates an instruction such as CFI, STI or POPF). 1705 1706In addition, the current state of the interrupt flag is indicated by the presence 1707or absence of the "D" (interrupt disabled) perf script flag. If the interrupt 1708flag is changed, then the "t" flag is also included i.e. 1709 1710 no flag, interrupts enabled IF=1 1711 t interrupts become disabled IF=1 -> IF=0 1712 D interrupts are disabled IF=0 1713 Dt interrupts become enabled IF=0 -> IF=1 1714 1715The intel-pt-events.py script illustrates how to access Event Trace information 1716using a Python script. 1717 1718 1719TNT Disable 1720----------- 1721 1722TNT packets are disabled using the "notnt" config term. e.g. 1723 1724 perf record -e intel_pt/notnt/u uname 1725 1726In that case the --itrace q option is forced because walking executable code 1727to reconstruct the control flow is not possible. 1728 1729 1730Emulated PTWRITE 1731---------------- 1732 1733Later perf tools support a method to emulate the ptwrite instruction, which 1734can be useful if hardware does not support the ptwrite instruction. 1735 1736Instead of using the ptwrite instruction, a function is used which produces 1737a trace that encodes the payload data into TNT packets. Here is an example 1738of the function: 1739 1740 #include <stdint.h> 1741 1742 void perf_emulate_ptwrite(uint64_t x) 1743 __attribute__((externally_visible, noipa, no_instrument_function, naked)); 1744 1745 #define PERF_EMULATE_PTWRITE_8_BITS \ 1746 "1: shl %rax\n" \ 1747 " jc 1f\n" \ 1748 "1: shl %rax\n" \ 1749 " jc 1f\n" \ 1750 "1: shl %rax\n" \ 1751 " jc 1f\n" \ 1752 "1: shl %rax\n" \ 1753 " jc 1f\n" \ 1754 "1: shl %rax\n" \ 1755 " jc 1f\n" \ 1756 "1: shl %rax\n" \ 1757 " jc 1f\n" \ 1758 "1: shl %rax\n" \ 1759 " jc 1f\n" \ 1760 "1: shl %rax\n" \ 1761 " jc 1f\n" 1762 1763 /* Undefined instruction */ 1764 #define PERF_EMULATE_PTWRITE_UD2 ".byte 0x0f, 0x0b\n" 1765 1766 #define PERF_EMULATE_PTWRITE_MAGIC PERF_EMULATE_PTWRITE_UD2 ".ascii \"perf,ptwrite \"\n" 1767 1768 void perf_emulate_ptwrite(uint64_t x __attribute__ ((__unused__))) 1769 { 1770 /* Assumes SysV ABI : x passed in rdi */ 1771 __asm__ volatile ( 1772 "jmp 1f\n" 1773 PERF_EMULATE_PTWRITE_MAGIC 1774 "1: mov %rdi, %rax\n" 1775 PERF_EMULATE_PTWRITE_8_BITS 1776 PERF_EMULATE_PTWRITE_8_BITS 1777 PERF_EMULATE_PTWRITE_8_BITS 1778 PERF_EMULATE_PTWRITE_8_BITS 1779 PERF_EMULATE_PTWRITE_8_BITS 1780 PERF_EMULATE_PTWRITE_8_BITS 1781 PERF_EMULATE_PTWRITE_8_BITS 1782 PERF_EMULATE_PTWRITE_8_BITS 1783 "1: ret\n" 1784 ); 1785 } 1786 1787For example, a test program with the function above: 1788 1789 #include <stdio.h> 1790 #include <stdint.h> 1791 #include <stdlib.h> 1792 1793 #include "perf_emulate_ptwrite.h" 1794 1795 int main(int argc, char *argv[]) 1796 { 1797 uint64_t x = 0; 1798 1799 if (argc > 1) 1800 x = strtoull(argv[1], NULL, 0); 1801 perf_emulate_ptwrite(x); 1802 return 0; 1803 } 1804 1805Can be compiled and traced: 1806 1807 $ gcc -Wall -Wextra -O3 -g -o eg_ptw eg_ptw.c 1808 $ perf record -e intel_pt//u ./eg_ptw 0x1234567890abcdef 1809 [ perf record: Woken up 1 times to write data ] 1810 [ perf record: Captured and wrote 0.017 MB perf.data ] 1811 $ perf script --itrace=ew 1812 eg_ptw 19875 [007] 8061.235912: ptwrite: IP: 0 payload: 0x1234567890abcdef 55701249a196 perf_emulate_ptwrite+0x16 (/home/user/eg_ptw) 1813 $ 1814 1815 1816EXAMPLE 1817------- 1818 1819Examples can be found on perf wiki page "Perf tools support for Intel® Processor Trace": 1820 1821https://perf.wiki.kernel.org/index.php/Perf_tools_support_for_Intel%C2%AE_Processor_Trace 1822 1823 1824SEE ALSO 1825-------- 1826 1827linkperf:perf-record[1], linkperf:perf-script[1], linkperf:perf-report[1], 1828linkperf:perf-inject[1] 1829