perf-stat(1) — Linux manual page


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

NAME         top

       perf-stat - Run a command and gather performance counter

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 symbolic or raw PMU event followed by an optional colon
               and a list of event modifiers, e.g., cpu-cycles:p. See
               the perf-list(1) man page for details on event modifiers.

           •   a symbolically formed event like pmu/param1=0x3,param2/
               where param1 and param2 are defined as formats for the
               PMU in /sys/bus/event_source/devices/<pmu>/format/*

                   'percore' is a event qualifier that sums up the event counts for both
                   hardware threads in a core. For example:
                   perf stat -A -a -e cpu/event,percore=1/,otherevent ...

           •   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)

       -b, --bpf-prog
           stat events on existing bpf program id (comma separated
           list), requiring root rights. bpftool-prog could be used to
           find program id all bpf programs in the system. For example:

               # bpftool prog | head -n 1
               17247: tracepoint  name sys_enter  tag 192d548b9d754067  gpl

               # perf stat -e cycles,instructions --bpf-prog 17247 --timeout 1000

               Performance counter stats for 'BPF program(s) 17247':

               85,967      cycles
               28,982      instructions              #    0.34  insn per cycle

               1.102235068 seconds time elapsed

       -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

                     -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
           locale. Enabled by default. Use "--no-big-num" to disable.
           Default setting can be changed with "perf config

       -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

       -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,

               $ 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.

       --for-each-cgroup name
           Expand event list for each cgroup in "name" (allow multiple
           cgroups separated by comma). It also support regex patterns
           to match multiple groups. This has same effect that repeating
           -e option and -G option for each event x name. This option
           cannot be used with -G/--cgroup option.

       -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

       --control=fifo:ctl-fifo[,ack-fifo], --control=fd:ctl-fd[,ack-fd]
           ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as
           follows. Listen on ctl-fd descriptor for command to control
           measurement (enable: enable events, disable: disable events).
           Measurements can be started with events disabled using
           --delay=-1 option. Optionally send control command completion
           (ack\n) to ack-fd descriptor to synchronize with the
           controlling process. Example of bash shell script to enable
           and disable events during measurements:



               test -p ${ctl_fifo} && unlink ${ctl_fifo}
               mkfifo ${ctl_fifo}
               exec {ctl_fd}<>${ctl_fifo}

               test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo}
               mkfifo ${ctl_ack_fifo}
               exec {ctl_fd_ack}<>${ctl_ack_fifo}

               perf stat -D -1 -e cpu-cycles -a -I 1000       \
                         --control fd:${ctl_fd},${ctl_fd_ack} \
                         -- sleep 30 &

               sleep 5  && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})"
               sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})"

               exec {ctl_fd_ack}>&-
               unlink ${ctl_ack_fifo}

               exec {ctl_fd}>&-
               unlink ${ctl_fifo}

               wait -n ${perf_pid}
               exit $?

       --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

       If the metric exists, it is calculated by the counts generated in
       this interval and the metric is printed after #.

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

           Aggregate counts per NUMA nodes for system-wide mode
           measurements. This is a useful mode to detect imbalance
           between NUMA nodes. To enable this mode, use --per-node in
           addition to -a. (system-wide).

       -D msecs, --delay msecs
           After starting the program, wait msecs before measuring (-1:
           start with events disabled). 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.

           By default, events to compute a metric are placed in weak
           groups. The group tries to enforce scheduling all or none of
           the events. The --metric-no-group option places events
           outside of groups and may increase the chance of the event
           being scheduled - leading to more accuracy. However, as
           events may not be scheduled together accuracy for metrics
           like instructions per cycle can be lower - as both metrics
           may no longer be being measured at the same time.

           By default metric events in different weak groups can be
           shared if one group contains all the events needed by
           another. In such cases one group will be eliminated reducing
           event multiplexing and making it so that certain groups of
           metrics sum to 100%. A downside to sharing a group is that
           the group may require multiplexing and so accuracy for a
           small group that need not have multiplexing is lowered. This
           option forbids the event merging logic from sharing events
           between groups and may be used to increase accuracy in this

           Don’t print output. This is useful with perf stat record
           below to only write data to the file.

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 processor die 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 complete top-down metrics 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

       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.

       This enables --metric-only, unless overridden with

       The following restrictions only apply to older Intel CPUs and
       Atom, on newer CPUs (IceLake and later) TopDown can be collected
       for any thread:

       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.

       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

           Print the top-down statistics that equal to or lower than the
           input level. It allows users to print the interested top-down
           metrics level instead of the complete top-down metrics.

       The availability of the top-down metrics level depends on the
       hardware. For example, Ice Lake only supports L1 top-down
       metrics. The Sapphire Rapids supports both L1 and L2 top-down

       Default: 0 means the max level that the current hardware support.
       Error out if the input is higher than the supported max level.

           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

       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

           Configure all used events to run in kernel space.

           Configure all used events to run in user space.

           The event modifier "percore" has supported to sum up the
           event counts for all hardware threads in a core and show the
           counts per core.

       This option with event modifier "percore" enabled also sums up
       the event counts for all hardware threads in a core but show the
       sum counts per hardware thread. This is essentially a replacement
       for the any bit and convenient for post processing.

           Print summary for interval mode (-I).

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

           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 2021-04-01.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-31.)  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                           2021-02-08                   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)