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

                   Note that the last two syntaxes support prefix and glob matching in
                   the PMU name to simplify creation of events across multiple instances
                   of the same type of PMU in large systems (e.g. memory controller PMUs).
                   Multiple PMU instances are typical for uncore PMUs, so the prefix
                   'uncore_' is also ignored when performing this match.

       -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

           Don’t 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.

           Display time for each run (-r option), in a table format, e.g.:

               $ perf stat --null -r 5 --table perf bench sched pipe

               Performance counter stats for 'perf bench sched pipe' (5 runs):

               # Table of individual measurements:
               5.189 (-0.293) #
               5.189 (-0.294) #
               5.186 (-0.296) #
               5.663 (+0.181) ##
               6.186 (+0.703) ####

               # Final result:
               5.483 +- 0.198 seconds time elapsed  ( +-  3.62% )

       -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. If the user wants to track multiple
           events for a specific cgroup, the user can use -e e1 -e e2 -G
           foo,foo or just use -e e1 -e e2 -G foo.

       If wanting to monitor, say, cycles for a cgroup and also for system
       wide, this command line can be used: perf stat -e cycles -G
       cgroup_name -a -e cycles.

       -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: 1ms) 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

       --interval-count times
           Print count deltas for fixed number of times. This option should
           be used together with "-I" option. example: perf stat -I 1000
           --interval-count 2 -e cycles -a

           Clear the screen before next interval.

       --timeout msecs
           Stop the perf stat session and print count deltas after N
           milliseconds (minimum: 10 ms). This option is not supported with
           the "-I" option. example: perf stat --time 2000 -e cycles -a

           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

       -M, --metrics
           Print metrics or metricgroups specified in a comma separated
           list. For a group all metrics from the group are added. The
           events from the metrics are automatically measured. See perf list
           output for the possble metrics and metricgroups.

       -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 overridden 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.

       When multiple events are created from a single event specification,
       stat will, by default, aggregate the event counts and show the result
       in a single row. This option disables that behavior and shows the
       individual events and counts.

       Multiple events are created from a single event specification when:
       1. Prefix or glob matching is used for the PMU name. 2. Aliases,
       which are listed immediately after the Kernel PMU events by perf
       list, are used.

           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

           Performance counter stats for 'make':

              83723.452481      task-clock:u (msec)       #    1.004 CPUs utilized
                         0      context-switches:u        #    0.000 K/sec
                         0      cpu-migrations:u          #    0.000 K/sec
                 3,228,188      page-faults:u             #    0.039 M/sec
           229,570,665,834      cycles:u                  #    2.742 GHz
           313,163,853,778      instructions:u            #    1.36  insn per cycle
            69,704,684,856      branches:u                #  832.559 M/sec
             2,078,861,393      branch-misses:u           #    2.98% of all branches

           83.409183620 seconds time elapsed

           74.684747000 seconds user
            8.739217000 seconds sys

TIMINGS         top

       As displayed in the example above we can display 3 types of timings.
       We always display the time the counters were enabled/alive:

           83.409183620 seconds time elapsed

       For workload sessions we also display time the workloads spent in
       user/system lands:

           74.684747000 seconds user
            8.739217000 seconds sys

       Those times are the very same as displayed by the time tool.

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
       2019-05-09.  (At that time, the date of the most recent commit that
       was found in the repository was 2019-05-08.)  If you discover any
       rendering problems in this HTML version 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 manual page), send a mail to

perf                             05/08/2019                     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)