1perf-stat(1) 2============ 3 4NAME 5---- 6perf-stat - Run a command and gather performance counter statistics 7 8SYNOPSIS 9-------- 10[verse] 11'perf stat' [-e <EVENT> | --event=EVENT] [-a] <command> 12'perf stat' [-e <EVENT> | --event=EVENT] [-a] -- <command> [<options>] 13'perf stat' [-e <EVENT> | --event=EVENT] [-a] record [-o file] -- <command> [<options>] 14'perf stat' report [-i file] 15 16DESCRIPTION 17----------- 18This command runs a command and gathers performance counter statistics 19from it. 20 21 22OPTIONS 23------- 24<command>...:: 25 Any command you can specify in a shell. 26 27record:: 28 See STAT RECORD. 29 30report:: 31 See STAT REPORT. 32 33-e:: 34--event=:: 35 Select the PMU event. Selection can be: 36 37 - a symbolic event name (use 'perf list' to list all events) 38 39 - a raw PMU event (eventsel+umask) in the form of rNNN where NNN is a 40 hexadecimal event descriptor. 41 42 - a symbolically formed event like 'pmu/param1=0x3,param2/' where 43 param1 and param2 are defined as formats for the PMU in 44 /sys/bus/event_source/devices/<pmu>/format/* 45 46 'percore' is a event qualifier that sums up the event counts for both 47 hardware threads in a core. For example: 48 perf stat -A -a -e cpu/event,percore=1/,otherevent ... 49 50 - a symbolically formed event like 'pmu/config=M,config1=N,config2=K/' 51 where M, N, K are numbers (in decimal, hex, octal format). 52 Acceptable values for each of 'config', 'config1' and 'config2' 53 parameters are defined by corresponding entries in 54 /sys/bus/event_source/devices/<pmu>/format/* 55 56 Note that the last two syntaxes support prefix and glob matching in 57 the PMU name to simplify creation of events across multiple instances 58 of the same type of PMU in large systems (e.g. memory controller PMUs). 59 Multiple PMU instances are typical for uncore PMUs, so the prefix 60 'uncore_' is also ignored when performing this match. 61 62 63-i:: 64--no-inherit:: 65 child tasks do not inherit counters 66-p:: 67--pid=<pid>:: 68 stat events on existing process id (comma separated list) 69 70-t:: 71--tid=<tid>:: 72 stat events on existing thread id (comma separated list) 73 74 75-a:: 76--all-cpus:: 77 system-wide collection from all CPUs (default if no target is specified) 78 79--no-scale:: 80 Don't scale/normalize counter values 81 82-d:: 83--detailed:: 84 print more detailed statistics, can be specified up to 3 times 85 86 -d: detailed events, L1 and LLC data cache 87 -d -d: more detailed events, dTLB and iTLB events 88 -d -d -d: very detailed events, adding prefetch events 89 90-r:: 91--repeat=<n>:: 92 repeat command and print average + stddev (max: 100). 0 means forever. 93 94-B:: 95--big-num:: 96 print large numbers with thousands' separators according to locale 97 98-C:: 99--cpu=:: 100Count only on the list of CPUs provided. Multiple CPUs can be provided as a 101comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2. 102In per-thread mode, this option is ignored. The -a option is still necessary 103to activate system-wide monitoring. Default is to count on all CPUs. 104 105-A:: 106--no-aggr:: 107Do not aggregate counts across all monitored CPUs. 108 109-n:: 110--null:: 111 null run - don't start any counters 112 113-v:: 114--verbose:: 115 be more verbose (show counter open errors, etc) 116 117-x SEP:: 118--field-separator SEP:: 119print counts using a CSV-style output to make it easy to import directly into 120spreadsheets. Columns are separated by the string specified in SEP. 121 122--table:: Display time for each run (-r option), in a table format, e.g.: 123 124 $ perf stat --null -r 5 --table perf bench sched pipe 125 126 Performance counter stats for 'perf bench sched pipe' (5 runs): 127 128 # Table of individual measurements: 129 5.189 (-0.293) # 130 5.189 (-0.294) # 131 5.186 (-0.296) # 132 5.663 (+0.181) ## 133 6.186 (+0.703) #### 134 135 # Final result: 136 5.483 +- 0.198 seconds time elapsed ( +- 3.62% ) 137 138-G name:: 139--cgroup name:: 140monitor only in the container (cgroup) called "name". This option is available only 141in per-cpu mode. The cgroup filesystem must be mounted. All threads belonging to 142container "name" are monitored when they run on the monitored CPUs. Multiple cgroups 143can be provided. Each cgroup is applied to the corresponding event, i.e., first cgroup 144to first event, second cgroup to second event and so on. It is possible to provide 145an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have 146corresponding events, i.e., they always refer to events defined earlier on the command 147line. If the user wants to track multiple events for a specific cgroup, the user can 148use '-e e1 -e e2 -G foo,foo' or just use '-e e1 -e e2 -G foo'. 149 150If wanting to monitor, say, 'cycles' for a cgroup and also for system wide, this 151command line can be used: 'perf stat -e cycles -G cgroup_name -a -e cycles'. 152 153-o file:: 154--output file:: 155Print the output into the designated file. 156 157--append:: 158Append to the output file designated with the -o option. Ignored if -o is not specified. 159 160--log-fd:: 161 162Log output to fd, instead of stderr. Complementary to --output, and mutually exclusive 163with it. --append may be used here. Examples: 164 3>results perf stat --log-fd 3 -- $cmd 165 3>>results perf stat --log-fd 3 --append -- $cmd 166 167--pre:: 168--post:: 169 Pre and post measurement hooks, e.g.: 170 171perf stat --repeat 10 --null --sync --pre 'make -s O=defconfig-build/clean' -- make -s -j64 O=defconfig-build/ bzImage 172 173-I msecs:: 174--interval-print msecs:: 175Print count deltas every N milliseconds (minimum: 1ms) 176The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals. Use with caution. 177 example: 'perf stat -I 1000 -e cycles -a sleep 5' 178 179--interval-count times:: 180Print count deltas for fixed number of times. 181This option should be used together with "-I" option. 182 example: 'perf stat -I 1000 --interval-count 2 -e cycles -a' 183 184--interval-clear:: 185Clear the screen before next interval. 186 187--timeout msecs:: 188Stop the 'perf stat' session and print count deltas after N milliseconds (minimum: 10 ms). 189This option is not supported with the "-I" option. 190 example: 'perf stat --time 2000 -e cycles -a' 191 192--metric-only:: 193Only print computed metrics. Print them in a single line. 194Don't show any raw values. Not supported with --per-thread. 195 196--per-socket:: 197Aggregate counts per processor socket for system-wide mode measurements. This 198is a useful mode to detect imbalance between sockets. To enable this mode, 199use --per-socket in addition to -a. (system-wide). The output includes the 200socket number and the number of online processors on that socket. This is 201useful to gauge the amount of aggregation. 202 203--per-die:: 204Aggregate counts per processor die for system-wide mode measurements. This 205is a useful mode to detect imbalance between dies. To enable this mode, 206use --per-die in addition to -a. (system-wide). The output includes the 207die number and the number of online processors on that die. This is 208useful to gauge the amount of aggregation. 209 210--per-core:: 211Aggregate counts per physical processor for system-wide mode measurements. This 212is a useful mode to detect imbalance between physical cores. To enable this mode, 213use --per-core in addition to -a. (system-wide). The output includes the 214core number and the number of online logical processors on that physical processor. 215 216--per-thread:: 217Aggregate counts per monitored threads, when monitoring threads (-t option) 218or processes (-p option). 219 220--per-node:: 221Aggregate counts per NUMA nodes for system-wide mode measurements. This 222is a useful mode to detect imbalance between NUMA nodes. To enable this 223mode, use --per-node in addition to -a. (system-wide). 224 225-D msecs:: 226--delay msecs:: 227After starting the program, wait msecs before measuring. This is useful to 228filter out the startup phase of the program, which is often very different. 229 230-T:: 231--transaction:: 232 233Print statistics of transactional execution if supported. 234 235STAT RECORD 236----------- 237Stores stat data into perf data file. 238 239-o file:: 240--output file:: 241Output file name. 242 243STAT REPORT 244----------- 245Reads and reports stat data from perf data file. 246 247-i file:: 248--input file:: 249Input file name. 250 251--per-socket:: 252Aggregate counts per processor socket for system-wide mode measurements. 253 254--per-die:: 255Aggregate counts per processor die for system-wide mode measurements. 256 257--per-core:: 258Aggregate counts per physical processor for system-wide mode measurements. 259 260-M:: 261--metrics:: 262Print metrics or metricgroups specified in a comma separated list. 263For a group all metrics from the group are added. 264The events from the metrics are automatically measured. 265See perf list output for the possble metrics and metricgroups. 266 267-A:: 268--no-aggr:: 269Do not aggregate counts across all monitored CPUs. 270 271--topdown:: 272Print top down level 1 metrics if supported by the CPU. This allows to 273determine bottle necks in the CPU pipeline for CPU bound workloads, 274by breaking the cycles consumed down into frontend bound, backend bound, 275bad speculation and retiring. 276 277Frontend bound means that the CPU cannot fetch and decode instructions fast 278enough. Backend bound means that computation or memory access is the bottle 279neck. Bad Speculation means that the CPU wasted cycles due to branch 280mispredictions and similar issues. Retiring means that the CPU computed without 281an apparently bottleneck. The bottleneck is only the real bottleneck 282if the workload is actually bound by the CPU and not by something else. 283 284For best results it is usually a good idea to use it with interval 285mode like -I 1000, as the bottleneck of workloads can change often. 286 287The top down metrics are collected per core instead of per 288CPU thread. Per core mode is automatically enabled 289and -a (global monitoring) is needed, requiring root rights or 290perf.perf_event_paranoid=-1. 291 292Topdown uses the full Performance Monitoring Unit, and needs 293disabling of the NMI watchdog (as root): 294echo 0 > /proc/sys/kernel/nmi_watchdog 295for best results. Otherwise the bottlenecks may be inconsistent 296on workload with changing phases. 297 298This enables --metric-only, unless overridden with --no-metric-only. 299 300To interpret the results it is usually needed to know on which 301CPUs the workload runs on. If needed the CPUs can be forced using 302taskset. 303 304--no-merge:: 305Do not merge results from same PMUs. 306 307When multiple events are created from a single event specification, 308stat will, by default, aggregate the event counts and show the result 309in a single row. This option disables that behavior and shows 310the individual events and counts. 311 312Multiple events are created from a single event specification when: 3131. Prefix or glob matching is used for the PMU name. 3142. Aliases, which are listed immediately after the Kernel PMU events 315 by perf list, are used. 316 317--smi-cost:: 318Measure SMI cost if msr/aperf/ and msr/smi/ events are supported. 319 320During the measurement, the /sys/device/cpu/freeze_on_smi will be set to 321freeze core counters on SMI. 322The aperf counter will not be effected by the setting. 323The cost of SMI can be measured by (aperf - unhalted core cycles). 324 325In practice, the percentages of SMI cycles is very useful for performance 326oriented analysis. --metric_only will be applied by default. 327The output is SMI cycles%, equals to (aperf - unhalted core cycles) / aperf 328 329Users who wants to get the actual value can apply --no-metric-only. 330 331--all-kernel:: 332Configure all used events to run in kernel space. 333 334--all-user:: 335Configure all used events to run in user space. 336 337EXAMPLES 338-------- 339 340$ perf stat -- make 341 342 Performance counter stats for 'make': 343 344 83723.452481 task-clock:u (msec) # 1.004 CPUs utilized 345 0 context-switches:u # 0.000 K/sec 346 0 cpu-migrations:u # 0.000 K/sec 347 3,228,188 page-faults:u # 0.039 M/sec 348 229,570,665,834 cycles:u # 2.742 GHz 349 313,163,853,778 instructions:u # 1.36 insn per cycle 350 69,704,684,856 branches:u # 832.559 M/sec 351 2,078,861,393 branch-misses:u # 2.98% of all branches 352 353 83.409183620 seconds time elapsed 354 355 74.684747000 seconds user 356 8.739217000 seconds sys 357 358TIMINGS 359------- 360As displayed in the example above we can display 3 types of timings. 361We always display the time the counters were enabled/alive: 362 363 83.409183620 seconds time elapsed 364 365For workload sessions we also display time the workloads spent in 366user/system lands: 367 368 74.684747000 seconds user 369 8.739217000 seconds sys 370 371Those times are the very same as displayed by the 'time' tool. 372 373CSV FORMAT 374---------- 375 376With -x, perf stat is able to output a not-quite-CSV format output 377Commas in the output are not put into "". To make it easy to parse 378it is recommended to use a different character like -x \; 379 380The fields are in this order: 381 382 - optional usec time stamp in fractions of second (with -I xxx) 383 - optional CPU, core, or socket identifier 384 - optional number of logical CPUs aggregated 385 - counter value 386 - unit of the counter value or empty 387 - event name 388 - run time of counter 389 - percentage of measurement time the counter was running 390 - optional variance if multiple values are collected with -r 391 - optional metric value 392 - optional unit of metric 393 394Additional metrics may be printed with all earlier fields being empty. 395 396SEE ALSO 397-------- 398linkperf:perf-top[1], linkperf:perf-list[1] 399