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 - a symbolically formed event like 'pmu/config=M,config1=N,config2=K/' 47 where M, N, K are numbers (in decimal, hex, octal format). 48 Acceptable values for each of 'config', 'config1' and 'config2' 49 parameters are defined by corresponding entries in 50 /sys/bus/event_source/devices/<pmu>/format/* 51 52-i:: 53--no-inherit:: 54 child tasks do not inherit counters 55-p:: 56--pid=<pid>:: 57 stat events on existing process id (comma separated list) 58 59-t:: 60--tid=<tid>:: 61 stat events on existing thread id (comma separated list) 62 63 64-a:: 65--all-cpus:: 66 system-wide collection from all CPUs (default if no target is specified) 67 68-c:: 69--scale:: 70 scale/normalize counter values 71 72-d:: 73--detailed:: 74 print more detailed statistics, can be specified up to 3 times 75 76 -d: detailed events, L1 and LLC data cache 77 -d -d: more detailed events, dTLB and iTLB events 78 -d -d -d: very detailed events, adding prefetch events 79 80-r:: 81--repeat=<n>:: 82 repeat command and print average + stddev (max: 100). 0 means forever. 83 84-B:: 85--big-num:: 86 print large numbers with thousands' separators according to locale 87 88-C:: 89--cpu=:: 90Count only on the list of CPUs provided. Multiple CPUs can be provided as a 91comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2. 92In per-thread mode, this option is ignored. The -a option is still necessary 93to activate system-wide monitoring. Default is to count on all CPUs. 94 95-A:: 96--no-aggr:: 97Do not aggregate counts across all monitored CPUs. 98 99-n:: 100--null:: 101 null run - don't start any counters 102 103-v:: 104--verbose:: 105 be more verbose (show counter open errors, etc) 106 107-x SEP:: 108--field-separator SEP:: 109print counts using a CSV-style output to make it easy to import directly into 110spreadsheets. Columns are separated by the string specified in SEP. 111 112-G name:: 113--cgroup name:: 114monitor only in the container (cgroup) called "name". This option is available only 115in per-cpu mode. The cgroup filesystem must be mounted. All threads belonging to 116container "name" are monitored when they run on the monitored CPUs. Multiple cgroups 117can be provided. Each cgroup is applied to the corresponding event, i.e., first cgroup 118to first event, second cgroup to second event and so on. It is possible to provide 119an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have 120corresponding events, i.e., they always refer to events defined earlier on the command 121line. 122 123-o file:: 124--output file:: 125Print the output into the designated file. 126 127--append:: 128Append to the output file designated with the -o option. Ignored if -o is not specified. 129 130--log-fd:: 131 132Log output to fd, instead of stderr. Complementary to --output, and mutually exclusive 133with it. --append may be used here. Examples: 134 3>results perf stat --log-fd 3 -- $cmd 135 3>>results perf stat --log-fd 3 --append -- $cmd 136 137--pre:: 138--post:: 139 Pre and post measurement hooks, e.g.: 140 141perf stat --repeat 10 --null --sync --pre 'make -s O=defconfig-build/clean' -- make -s -j64 O=defconfig-build/ bzImage 142 143-I msecs:: 144--interval-print msecs:: 145Print count deltas every N milliseconds (minimum: 10ms) 146The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals. Use with caution. 147 example: 'perf stat -I 1000 -e cycles -a sleep 5' 148 149--interval-count times:: 150Print count deltas for fixed number of times. 151This option should be used together with "-I" option. 152 example: 'perf stat -I 1000 --interval-count 2 -e cycles -a' 153 154--timeout msecs:: 155Stop the 'perf stat' session and print count deltas after N milliseconds (minimum: 10 ms). 156This option is not supported with the "-I" option. 157 example: 'perf stat --time 2000 -e cycles -a' 158 159--metric-only:: 160Only print computed metrics. Print them in a single line. 161Don't show any raw values. Not supported with --per-thread. 162 163--per-socket:: 164Aggregate counts per processor socket for system-wide mode measurements. This 165is a useful mode to detect imbalance between sockets. To enable this mode, 166use --per-socket in addition to -a. (system-wide). The output includes the 167socket number and the number of online processors on that socket. This is 168useful to gauge the amount of aggregation. 169 170--per-core:: 171Aggregate counts per physical processor for system-wide mode measurements. This 172is a useful mode to detect imbalance between physical cores. To enable this mode, 173use --per-core in addition to -a. (system-wide). The output includes the 174core number and the number of online logical processors on that physical processor. 175 176--per-thread:: 177Aggregate counts per monitored threads, when monitoring threads (-t option) 178or processes (-p option). 179 180-D msecs:: 181--delay msecs:: 182After starting the program, wait msecs before measuring. This is useful to 183filter out the startup phase of the program, which is often very different. 184 185-T:: 186--transaction:: 187 188Print statistics of transactional execution if supported. 189 190STAT RECORD 191----------- 192Stores stat data into perf data file. 193 194-o file:: 195--output file:: 196Output file name. 197 198STAT REPORT 199----------- 200Reads and reports stat data from perf data file. 201 202-i file:: 203--input file:: 204Input file name. 205 206--per-socket:: 207Aggregate counts per processor socket for system-wide mode measurements. 208 209--per-core:: 210Aggregate counts per physical processor for system-wide mode measurements. 211 212-M:: 213--metrics:: 214Print metrics or metricgroups specified in a comma separated list. 215For a group all metrics from the group are added. 216The events from the metrics are automatically measured. 217See perf list output for the possble metrics and metricgroups. 218 219-A:: 220--no-aggr:: 221Do not aggregate counts across all monitored CPUs. 222 223--topdown:: 224Print top down level 1 metrics if supported by the CPU. This allows to 225determine bottle necks in the CPU pipeline for CPU bound workloads, 226by breaking the cycles consumed down into frontend bound, backend bound, 227bad speculation and retiring. 228 229Frontend bound means that the CPU cannot fetch and decode instructions fast 230enough. Backend bound means that computation or memory access is the bottle 231neck. Bad Speculation means that the CPU wasted cycles due to branch 232mispredictions and similar issues. Retiring means that the CPU computed without 233an apparently bottleneck. The bottleneck is only the real bottleneck 234if the workload is actually bound by the CPU and not by something else. 235 236For best results it is usually a good idea to use it with interval 237mode like -I 1000, as the bottleneck of workloads can change often. 238 239The top down metrics are collected per core instead of per 240CPU thread. Per core mode is automatically enabled 241and -a (global monitoring) is needed, requiring root rights or 242perf.perf_event_paranoid=-1. 243 244Topdown uses the full Performance Monitoring Unit, and needs 245disabling of the NMI watchdog (as root): 246echo 0 > /proc/sys/kernel/nmi_watchdog 247for best results. Otherwise the bottlenecks may be inconsistent 248on workload with changing phases. 249 250This enables --metric-only, unless overriden with --no-metric-only. 251 252To interpret the results it is usually needed to know on which 253CPUs the workload runs on. If needed the CPUs can be forced using 254taskset. 255 256--no-merge:: 257Do not merge results from same PMUs. 258 259--smi-cost:: 260Measure SMI cost if msr/aperf/ and msr/smi/ events are supported. 261 262During the measurement, the /sys/device/cpu/freeze_on_smi will be set to 263freeze core counters on SMI. 264The aperf counter will not be effected by the setting. 265The cost of SMI can be measured by (aperf - unhalted core cycles). 266 267In practice, the percentages of SMI cycles is very useful for performance 268oriented analysis. --metric_only will be applied by default. 269The output is SMI cycles%, equals to (aperf - unhalted core cycles) / aperf 270 271Users who wants to get the actual value can apply --no-metric-only. 272 273EXAMPLES 274-------- 275 276$ perf stat -- make -j 277 278 Performance counter stats for 'make -j': 279 280 8117.370256 task clock ticks # 11.281 CPU utilization factor 281 678 context switches # 0.000 M/sec 282 133 CPU migrations # 0.000 M/sec 283 235724 pagefaults # 0.029 M/sec 284 24821162526 CPU cycles # 3057.784 M/sec 285 18687303457 instructions # 2302.138 M/sec 286 172158895 cache references # 21.209 M/sec 287 27075259 cache misses # 3.335 M/sec 288 289 Wall-clock time elapsed: 719.554352 msecs 290 291CSV FORMAT 292---------- 293 294With -x, perf stat is able to output a not-quite-CSV format output 295Commas in the output are not put into "". To make it easy to parse 296it is recommended to use a different character like -x \; 297 298The fields are in this order: 299 300 - optional usec time stamp in fractions of second (with -I xxx) 301 - optional CPU, core, or socket identifier 302 - optional number of logical CPUs aggregated 303 - counter value 304 - unit of the counter value or empty 305 - event name 306 - run time of counter 307 - percentage of measurement time the counter was running 308 - optional variance if multiple values are collected with -r 309 - optional metric value 310 - optional unit of metric 311 312Additional metrics may be printed with all earlier fields being empty. 313 314SEE ALSO 315-------- 316linkperf:perf-top[1], linkperf:perf-list[1] 317