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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | STAT RECORD | STAT REPORT | EXAMPLES | TIMINGS | CSV FORMAT | SEE ALSO | COLOPHON |
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PERF-STAT(1) perf Manual PERF-STAT(1)
perf-stat - Run a command and gather performance counter
statistics
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]
This command runs a command and gathers performance counter
statistics from it.
<command>...
Any command you can specify in a shell.
record
See STAT RECORD.
report
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
/sys/bus/event_source/devices/<pmu>/format/*
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
specified)
--no-scale
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
forever.
-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
stat.big-num=false".
-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.
--table
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.
--for-each-cgroup name
Expand event list for each cgroup in "name" (allow multiple
cgroups separated by comma). 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
Append to the output file designated with the -o option.
Ignored if -o is not specified.
--log-fd
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 — $cmd
--control=fifo:ctl-fifo[,ack-fifo], --control=fd:ctl-fd[,ack-fd]
ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as
follows. Listen on ctl-fd descriptor for command to control
measurement (enable: enable events, disable: disable events).
Measurements can be started with events disabled using
--delay=-1 option. Optionally send control command completion
(ack\n) to ack-fd descriptor to synchronize with the
controlling process. Example of bash shell script to enable
and disable events during measurements:
#!/bin/bash
ctl_dir=/tmp/
ctl_fifo=${ctl_dir}perf_ctl.fifo
test -p ${ctl_fifo} && unlink ${ctl_fifo}
mkfifo ${ctl_fifo}
exec {ctl_fd}<>${ctl_fifo}
ctl_ack_fifo=${ctl_dir}perf_ctl_ack.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 &
perf_pid=$!
sleep 5 && echo 'enable' >&${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
--interval-clear
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
--metric-only
Only print computed metrics. Print them in a single line.
Don’t show any raw values. Not supported with --per-thread.
--per-socket
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.
--per-die
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.
--per-core
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.
--per-thread
Aggregate counts per monitored threads, when monitoring
threads (-t option) or processes (-p option).
--per-node
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.
--metric-no-group
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.
--metric-no-merge
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
case.
Stores stat data into perf data file.
-o file, --output file
Output file name.
Reads and reports stat data from perf data file.
-i file, --input file
Input file name.
--per-socket
Aggregate counts per processor socket for system-wide mode
measurements.
--per-die
Aggregate counts per processor die for system-wide mode
measurements.
--per-core
Aggregate counts per physical processor for system-wide mode
measurements.
-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.
--topdown
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.
This enables --metric-only, unless overridden with
--no-metric-only.
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
perf.perf_event_paranoid=-1.
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
taskset.
--no-merge
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.
--smi-cost
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.
--all-kernel
Configure all used events to run in kernel space.
--all-user
Configure all used events to run in user space.
--percore-show-thread
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.
--summary
Print summary for interval mode (-I).
$ 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
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.
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
empty.
perf-top(1), perf-list(1)
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
⟨https://perf.wiki.kernel.org/index.php/Main_Page⟩. If you have a
bug report for this manual page, send it to
linux-kernel@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git⟩
on 2020-12-18. (At that time, the date of the most recent commit
that was found in the repository was 2020-12-17.) 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 man-pages@man7.org
perf 2020-09-28 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)
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