perf-stat(1)
NAME
perf-stat - Run a command and gather performance counter statistics
SYNOPSIS
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
This command runs a command and gathers performance counter statistics from it.
OPTIONS
<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_sources/devices/<pmu>/format/*
* 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_sources/devices/<pmu>/format/*
-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
-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
forever.
-B, --big-num
print large numbers with thousands' separators according to locale
-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 in system-wide
mode (-a). This option is only valid in system-wide mode.
-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
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
--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
--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-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).
-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
Stores stat data into perf data file.
-o file, --output file
Output file name.
STAT REPORT
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-core
Aggregate counts per physical processor for system-wide mode
measurements.
-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 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.
EXAMPLES
$ 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
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.
SEE ALSO
perf-top(1), perf-list(1)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
