PERF-STAT(1)                     perf Manual                    PERF-STAT(1)

NAME         top

       perf-stat - Run a command and gather performance counter statistics

SYNOPSIS         top

       perf stat [-e <EVENT> | --event=EVENT] [-a] <command>
       perf stat [-e <EVENT> | --event=EVENT] [-a] — <command> [<options>]
       perf stat [-e <EVENT> | --event=EVENT] [-a] record [-o file] — <command> [<options>]
       perf stat report [-i file]

DESCRIPTION         top

       This command runs a command and gathers performance counter
       statistics from it.

OPTIONS         top

           Any command you can specify in a shell.

           See STAT RECORD.

           See STAT REPORT.

       -e, --event=
           Select the PMU event. Selection can be:

           ·   a symbolic event name (use perf list to list all events)

           ·   a raw PMU event (eventsel+umask) in the form of rNNN where
               NNN is a hexadecimal event descriptor.

           ·   a symbolically formed event like pmu/param1=0x3,param2/ where
               param1 and param2 are defined as formats for the PMU in

           ·   a symbolically formed event like
               pmu/config=M,config1=N,config2=K/ where M, N, K are numbers
               (in decimal, hex, octal format). Acceptable values for each
               of config, config1 and config2 parameters are defined by
               corresponding entries in

       -i, --no-inherit
           child tasks do not inherit counters

       -p, --pid=<pid>
           stat events on existing process id (comma separated list)

       -t, --tid=<tid>
           stat events on existing thread id (comma separated list)

       -a, --all-cpus
           system-wide collection from all CPUs (default if no target is

       -c, --scale
           scale/normalize counter values

       -d, --detailed
           print more detailed statistics, can be specified up to 3 times

                     -d:          detailed events, L1 and LLC data cache
                  -d -d:     more detailed events, dTLB and iTLB events
               -d -d -d:     very detailed events, adding prefetch events

       -r, --repeat=<n>
           repeat command and print average + stddev (max: 100). 0 means

       -B, --big-num
           print large numbers with thousands' separators according to

       -C, --cpu=
           Count only on the list of CPUs provided. Multiple CPUs can be
           provided as a comma-separated list with no space: 0,1. Ranges of
           CPUs are specified with -: 0-2. In per-thread mode, this option
           is ignored. The -a option is still necessary to activate
           system-wide monitoring. Default is to count on all CPUs.

       -A, --no-aggr
           Do not aggregate counts across all monitored CPUs.

       -n, --null
           null run - don’t start any counters

       -v, --verbose
           be more verbose (show counter open errors, etc)

       -x SEP, --field-separator SEP
           print counts using a CSV-style output to make it easy to import
           directly into spreadsheets. Columns are separated by the string
           specified in SEP.

       -G name, --cgroup name
           monitor only in the container (cgroup) called "name". This option
           is available only in per-cpu mode. The cgroup filesystem must be
           mounted. All threads belonging to container "name" are monitored
           when they run on the monitored CPUs. Multiple cgroups can be
           provided. Each cgroup is applied to the corresponding event,
           i.e., first cgroup to first event, second cgroup to second event
           and so on. It is possible to provide an empty cgroup (monitor all
           the time) using, e.g., -G foo,,bar. Cgroups must have
           corresponding events, i.e., they always refer to events defined
           earlier on the command line.

       -o file, --output file
           Print the output into the designated file.

           Append to the output file designated with the -o option. Ignored
           if -o is not specified.

           Log output to fd, instead of stderr. Complementary to --output,
           and mutually exclusive with it. --append may be used here.
           Examples: 3>results perf stat --log-fd 3  — $cmd 3>>results perf
           stat --log-fd 3 --append — $cmd

       --pre, --post
           Pre and post measurement hooks, e.g.:

       perf stat --repeat 10 --null --sync --pre make -s
       O=defconfig-build/clean — make -s -j64 O=defconfig-build/ bzImage

       -I msecs, --interval-print msecs
           Print count deltas every N milliseconds (minimum: 10ms) The
           overhead percentage could be high in some cases, for instance
           with small, sub 100ms intervals. Use with caution. example: perf
           stat -I 1000 -e cycles -a sleep 5

           Only print computed metrics. Print them in a single line. Don’t
           show any raw values. Not supported with --per-thread.

           Aggregate counts per processor socket for system-wide mode
           measurements. This is a useful mode to detect imbalance between
           sockets. To enable this mode, use --per-socket in addition to -a.
           (system-wide). The output includes the socket number and the
           number of online processors on that socket. This is useful to
           gauge the amount of aggregation.

           Aggregate counts per physical processor for system-wide mode
           measurements. This is a useful mode to detect imbalance between
           physical cores. To enable this mode, use --per-core in addition
           to -a. (system-wide). The output includes the core number and the
           number of online logical processors on that physical processor.

           Aggregate counts per monitored threads, when monitoring threads
           (-t option) or processes (-p option).

       -D msecs, --delay msecs
           After starting the program, wait msecs before measuring. This is
           useful to filter out the startup phase of the program, which is
           often very different.

       -T, --transaction
           Print statistics of transactional execution if supported.

STAT RECORD         top

       Stores stat data into perf data file.

       -o file, --output file
           Output file name.

STAT REPORT         top

       Reads and reports stat data from perf data file.

       -i file, --input file
           Input file name.

           Aggregate counts per processor socket for system-wide mode

           Aggregate counts per physical processor for system-wide mode

       -A, --no-aggr
           Do not aggregate counts across all monitored CPUs.

           Print top down level 1 metrics if supported by the CPU. This
           allows to determine bottle necks in the CPU pipeline for CPU
           bound workloads, by breaking the cycles consumed down into
           frontend bound, backend bound, bad speculation and retiring.

       Frontend bound means that the CPU cannot fetch and decode
       instructions fast enough. Backend bound means that computation or
       memory access is the bottle neck. Bad Speculation means that the CPU
       wasted cycles due to branch mispredictions and similar issues.
       Retiring means that the CPU computed without an apparently
       bottleneck. The bottleneck is only the real bottleneck if the
       workload is actually bound by the CPU and not by something else.

       For best results it is usually a good idea to use it with interval
       mode like -I 1000, as the bottleneck of workloads can change often.

       The top down metrics are collected per core instead of per CPU
       thread. Per core mode is automatically enabled and -a (global
       monitoring) is needed, requiring root rights or

       Topdown uses the full Performance Monitoring Unit, and needs
       disabling of the NMI watchdog (as root): echo 0 >
       /proc/sys/kernel/nmi_watchdog for best results. Otherwise the
       bottlenecks may be inconsistent on workload with changing phases.

       This enables --metric-only, unless overriden with --no-metric-only.

       To interpret the results it is usually needed to know on which CPUs
       the workload runs on. If needed the CPUs can be forced using taskset.

           Do not merge results from same PMUs.

           Measure SMI cost if msr/aperf/ and msr/smi/ events are supported.

       During the measurement, the /sys/device/cpu/freeze_on_smi will be set
       to freeze core counters on SMI. The aperf counter will not be
       effected by the setting. The cost of SMI can be measured by (aperf -
       unhalted core cycles).

       In practice, the percentages of SMI cycles is very useful for
       performance oriented analysis. --metric_only will be applied by
       default. The output is SMI cycles%, equals to (aperf - unhalted core
       cycles) / aperf

       Users who wants to get the actual value can apply --no-metric-only.

EXAMPLES         top

       $ perf stat — make -j

           Performance counter stats for 'make -j':

           8117.370256  task clock ticks     #      11.281 CPU utilization factor
                   678  context switches     #       0.000 M/sec
                   133  CPU migrations       #       0.000 M/sec
                235724  pagefaults           #       0.029 M/sec
           24821162526  CPU cycles           #    3057.784 M/sec
           18687303457  instructions         #    2302.138 M/sec
             172158895  cache references     #      21.209 M/sec
              27075259  cache misses         #       3.335 M/sec

           Wall-clock time elapsed:   719.554352 msecs

CSV FORMAT         top

       With -x, perf stat is able to output a not-quite-CSV format output
       Commas in the output are not put into "". To make it easy to parse it
       is recommended to use a different character like -x \;

       The fields are in this order:

       ·   optional usec time stamp in fractions of second (with -I xxx)

       ·   optional CPU, core, or socket identifier

       ·   optional number of logical CPUs aggregated

       ·   counter value

       ·   unit of the counter value or empty

       ·   event name

       ·   run time of counter

       ·   percentage of measurement time the counter was running

       ·   optional variance if multiple values are collected with -r

       ·   optional metric value

       ·   optional unit of metric

       Additional metrics may be printed with all earlier fields being

SEE ALSO         top

       perf-top(1), perf-list(1)

COLOPHON         top

       This page is part of the perf (Performance analysis tools for Linux
       (in Linux source tree)) project.  Information about the project can
       be found at ⟨⟩.  If
       you have a bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository 
       ⟨⟩ on
       2017-09-15.  If you discover any rendering problems in this HTML ver‐
       sion of the page, or you believe there is a better or more up-to-date
       source for the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original man‐
       ual page), send a mail to

perf                             09/14/2017                     PERF-STAT(1)

Pages that refer to this page: perf(1)perf-kvm(1)perf-list(1)perf-record(1)perf-report(1)perf-top(1)