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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | STAT RECORD | STAT REPORT | EXAMPLES | TIMINGS | CSV FORMAT | SEE ALSO | COLOPHON |
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 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.
-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 — $cmd
--control fd:ctl-fd[,ack-fd] Listen on ctl-fd descriptor for command
to control measurement (enable: enable events, disable: disable
events). Measurements can be started with events disabled using
--delay=-1 option. Optionally send control command completion (ack\n)
to ack-fd descriptor to synchronize with the controlling process.
Example of bash shell script to enable and disable events during
measurements:
#!/bin/bash
ctl_dir=/tmp/
perf stat -D -1 -e cpu-cycles -a -I 1000 \ — sleep 30 & perf_pid=$!
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.
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.
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.
--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.
$ 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
2020-08-13. (At that time, the date of the most recent commit that
was found in the repository was 2020-08-12.) 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 2020-08-04 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)