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-core:: 204Aggregate counts per physical processor for system-wide mode measurements. This 205is a useful mode to detect imbalance between physical cores. To enable this mode, 206use --per-core in addition to -a. (system-wide). The output includes the 207core number and the number of online logical processors on that physical processor. 208 209--per-thread:: 210Aggregate counts per monitored threads, when monitoring threads (-t option) 211or processes (-p option). 212 213-D msecs:: 214--delay msecs:: 215After starting the program, wait msecs before measuring. This is useful to 216filter out the startup phase of the program, which is often very different. 217 218-T:: 219--transaction:: 220 221Print statistics of transactional execution if supported. 222 223STAT RECORD 224----------- 225Stores stat data into perf data file. 226 227-o file:: 228--output file:: 229Output file name. 230 231STAT REPORT 232----------- 233Reads and reports stat data from perf data file. 234 235-i file:: 236--input file:: 237Input file name. 238 239--per-socket:: 240Aggregate counts per processor socket for system-wide mode measurements. 241 242--per-core:: 243Aggregate counts per physical processor for system-wide mode measurements. 244 245-M:: 246--metrics:: 247Print metrics or metricgroups specified in a comma separated list. 248For a group all metrics from the group are added. 249The events from the metrics are automatically measured. 250See perf list output for the possble metrics and metricgroups. 251 252-A:: 253--no-aggr:: 254Do not aggregate counts across all monitored CPUs. 255 256--topdown:: 257Print top down level 1 metrics if supported by the CPU. This allows to 258determine bottle necks in the CPU pipeline for CPU bound workloads, 259by breaking the cycles consumed down into frontend bound, backend bound, 260bad speculation and retiring. 261 262Frontend bound means that the CPU cannot fetch and decode instructions fast 263enough. Backend bound means that computation or memory access is the bottle 264neck. Bad Speculation means that the CPU wasted cycles due to branch 265mispredictions and similar issues. Retiring means that the CPU computed without 266an apparently bottleneck. The bottleneck is only the real bottleneck 267if the workload is actually bound by the CPU and not by something else. 268 269For best results it is usually a good idea to use it with interval 270mode like -I 1000, as the bottleneck of workloads can change often. 271 272The top down metrics are collected per core instead of per 273CPU thread. Per core mode is automatically enabled 274and -a (global monitoring) is needed, requiring root rights or 275perf.perf_event_paranoid=-1. 276 277Topdown uses the full Performance Monitoring Unit, and needs 278disabling of the NMI watchdog (as root): 279echo 0 > /proc/sys/kernel/nmi_watchdog 280for best results. Otherwise the bottlenecks may be inconsistent 281on workload with changing phases. 282 283This enables --metric-only, unless overridden with --no-metric-only. 284 285To interpret the results it is usually needed to know on which 286CPUs the workload runs on. If needed the CPUs can be forced using 287taskset. 288 289--no-merge:: 290Do not merge results from same PMUs. 291 292When multiple events are created from a single event specification, 293stat will, by default, aggregate the event counts and show the result 294in a single row. This option disables that behavior and shows 295the individual events and counts. 296 297Multiple events are created from a single event specification when: 2981. Prefix or glob matching is used for the PMU name. 2992. Aliases, which are listed immediately after the Kernel PMU events 300 by perf list, are used. 301 302--smi-cost:: 303Measure SMI cost if msr/aperf/ and msr/smi/ events are supported. 304 305During the measurement, the /sys/device/cpu/freeze_on_smi will be set to 306freeze core counters on SMI. 307The aperf counter will not be effected by the setting. 308The cost of SMI can be measured by (aperf - unhalted core cycles). 309 310In practice, the percentages of SMI cycles is very useful for performance 311oriented analysis. --metric_only will be applied by default. 312The output is SMI cycles%, equals to (aperf - unhalted core cycles) / aperf 313 314Users who wants to get the actual value can apply --no-metric-only. 315 316EXAMPLES 317-------- 318 319$ perf stat -- make 320 321 Performance counter stats for 'make': 322 323 83723.452481 task-clock:u (msec) # 1.004 CPUs utilized 324 0 context-switches:u # 0.000 K/sec 325 0 cpu-migrations:u # 0.000 K/sec 326 3,228,188 page-faults:u # 0.039 M/sec 327 229,570,665,834 cycles:u # 2.742 GHz 328 313,163,853,778 instructions:u # 1.36 insn per cycle 329 69,704,684,856 branches:u # 832.559 M/sec 330 2,078,861,393 branch-misses:u # 2.98% of all branches 331 332 83.409183620 seconds time elapsed 333 334 74.684747000 seconds user 335 8.739217000 seconds sys 336 337TIMINGS 338------- 339As displayed in the example above we can display 3 types of timings. 340We always display the time the counters were enabled/alive: 341 342 83.409183620 seconds time elapsed 343 344For workload sessions we also display time the workloads spent in 345user/system lands: 346 347 74.684747000 seconds user 348 8.739217000 seconds sys 349 350Those times are the very same as displayed by the 'time' tool. 351 352CSV FORMAT 353---------- 354 355With -x, perf stat is able to output a not-quite-CSV format output 356Commas in the output are not put into "". To make it easy to parse 357it is recommended to use a different character like -x \; 358 359The fields are in this order: 360 361 - optional usec time stamp in fractions of second (with -I xxx) 362 - optional CPU, core, or socket identifier 363 - optional number of logical CPUs aggregated 364 - counter value 365 - unit of the counter value or empty 366 - event name 367 - run time of counter 368 - percentage of measurement time the counter was running 369 - optional variance if multiple values are collected with -r 370 - optional metric value 371 - optional unit of metric 372 373Additional metrics may be printed with all earlier fields being empty. 374 375SEE ALSO 376-------- 377linkperf:perf-top[1], linkperf:perf-list[1] 378