283 lines
8.8 KiB
Text
283 lines
8.8 KiB
Text
perf-stat(1)
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============
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NAME
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----
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perf-stat - Run a command and gather performance counter statistics
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SYNOPSIS
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--------
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[verse]
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'perf stat' [-e <EVENT> | --event=EVENT] [-a] <command>
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'perf stat' [-e <EVENT> | --event=EVENT] [-a] -- <command> [<options>]
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'perf stat' [-e <EVENT> | --event=EVENT] [-a] record [-o file] -- <command> [<options>]
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'perf stat' report [-i file]
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DESCRIPTION
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-----------
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This command runs a command and gathers performance counter statistics
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from it.
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OPTIONS
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-------
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<command>...::
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Any command you can specify in a shell.
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record::
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See STAT RECORD.
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report::
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See STAT REPORT.
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-e::
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--event=::
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Select the PMU event. Selection can be:
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- a symbolic event name (use 'perf list' to list all events)
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- a raw PMU event (eventsel+umask) in the form of rNNN where NNN is a
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hexadecimal event descriptor.
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- a symbolically formed event like 'pmu/param1=0x3,param2/' where
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param1 and param2 are defined as formats for the PMU in
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/sys/bus/event_sources/devices/<pmu>/format/*
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- a symbolically formed event like 'pmu/config=M,config1=N,config2=K/'
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where M, N, K are numbers (in decimal, hex, octal format).
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Acceptable values for each of 'config', 'config1' and 'config2'
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parameters are defined by corresponding entries in
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/sys/bus/event_sources/devices/<pmu>/format/*
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-i::
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--no-inherit::
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child tasks do not inherit counters
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-p::
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--pid=<pid>::
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stat events on existing process id (comma separated list)
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-t::
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--tid=<tid>::
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stat events on existing thread id (comma separated list)
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-a::
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--all-cpus::
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system-wide collection from all CPUs
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-c::
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--scale::
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scale/normalize counter values
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-d::
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--detailed::
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print more detailed statistics, can be specified up to 3 times
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-d: detailed events, L1 and LLC data cache
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-d -d: more detailed events, dTLB and iTLB events
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-d -d -d: very detailed events, adding prefetch events
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-r::
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--repeat=<n>::
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repeat command and print average + stddev (max: 100). 0 means forever.
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-B::
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--big-num::
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print large numbers with thousands' separators according to locale
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-C::
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--cpu=::
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Count only on the list of CPUs provided. Multiple CPUs can be provided as a
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comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2.
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In per-thread mode, this option is ignored. The -a option is still necessary
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to activate system-wide monitoring. Default is to count on all CPUs.
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-A::
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--no-aggr::
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Do not aggregate counts across all monitored CPUs in system-wide mode (-a).
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This option is only valid in system-wide mode.
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-n::
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--null::
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null run - don't start any counters
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-v::
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--verbose::
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be more verbose (show counter open errors, etc)
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-x SEP::
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--field-separator SEP::
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print counts using a CSV-style output to make it easy to import directly into
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spreadsheets. Columns are separated by the string specified in SEP.
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-G name::
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--cgroup name::
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monitor only in the container (cgroup) called "name". This option is available only
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in per-cpu mode. The cgroup filesystem must be mounted. All threads belonging to
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container "name" are monitored when they run on the monitored CPUs. Multiple cgroups
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can be provided. Each cgroup is applied to the corresponding event, i.e., first cgroup
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to first event, second cgroup to second event and so on. It is possible to provide
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an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have
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corresponding events, i.e., they always refer to events defined earlier on the command
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line.
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-o file::
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--output file::
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Print the output into the designated file.
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--append::
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Append to the output file designated with the -o option. Ignored if -o is not specified.
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--log-fd::
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Log output to fd, instead of stderr. Complementary to --output, and mutually exclusive
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with it. --append may be used here. Examples:
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3>results perf stat --log-fd 3 -- $cmd
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3>>results perf stat --log-fd 3 --append -- $cmd
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--pre::
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--post::
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Pre and post measurement hooks, e.g.:
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perf stat --repeat 10 --null --sync --pre 'make -s O=defconfig-build/clean' -- make -s -j64 O=defconfig-build/ bzImage
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-I msecs::
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--interval-print msecs::
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Print count deltas every N milliseconds (minimum: 10ms)
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The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals. Use with caution.
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example: 'perf stat -I 1000 -e cycles -a sleep 5'
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--metric-only::
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Only print computed metrics. Print them in a single line.
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Don't show any raw values. Not supported with --per-thread.
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--per-socket::
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Aggregate counts per processor socket for system-wide mode measurements. This
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is a useful mode to detect imbalance between sockets. To enable this mode,
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use --per-socket in addition to -a. (system-wide). The output includes the
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socket number and the number of online processors on that socket. This is
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useful to gauge the amount of aggregation.
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--per-core::
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Aggregate counts per physical processor for system-wide mode measurements. This
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is a useful mode to detect imbalance between physical cores. To enable this mode,
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use --per-core in addition to -a. (system-wide). The output includes the
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core number and the number of online logical processors on that physical processor.
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--per-thread::
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Aggregate counts per monitored threads, when monitoring threads (-t option)
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or processes (-p option).
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-D msecs::
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--delay msecs::
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After starting the program, wait msecs before measuring. This is useful to
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filter out the startup phase of the program, which is often very different.
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-T::
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--transaction::
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Print statistics of transactional execution if supported.
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STAT RECORD
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-----------
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Stores stat data into perf data file.
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-o file::
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--output file::
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Output file name.
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STAT REPORT
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-----------
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Reads and reports stat data from perf data file.
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-i file::
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--input file::
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Input file name.
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--per-socket::
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Aggregate counts per processor socket for system-wide mode measurements.
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--per-core::
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Aggregate counts per physical processor for system-wide mode measurements.
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-A::
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--no-aggr::
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Do not aggregate counts across all monitored CPUs.
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--topdown::
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Print top down level 1 metrics if supported by the CPU. This allows to
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determine bottle necks in the CPU pipeline for CPU bound workloads,
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by breaking the cycles consumed down into frontend bound, backend bound,
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bad speculation and retiring.
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Frontend bound means that the CPU cannot fetch and decode instructions fast
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enough. Backend bound means that computation or memory access is the bottle
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neck. Bad Speculation means that the CPU wasted cycles due to branch
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mispredictions and similar issues. Retiring means that the CPU computed without
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an apparently bottleneck. The bottleneck is only the real bottleneck
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if the workload is actually bound by the CPU and not by something else.
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For best results it is usually a good idea to use it with interval
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mode like -I 1000, as the bottleneck of workloads can change often.
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The top down metrics are collected per core instead of per
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CPU thread. Per core mode is automatically enabled
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and -a (global monitoring) is needed, requiring root rights or
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perf.perf_event_paranoid=-1.
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Topdown uses the full Performance Monitoring Unit, and needs
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disabling of the NMI watchdog (as root):
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echo 0 > /proc/sys/kernel/nmi_watchdog
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for best results. Otherwise the bottlenecks may be inconsistent
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on workload with changing phases.
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This enables --metric-only, unless overriden with --no-metric-only.
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To interpret the results it is usually needed to know on which
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CPUs the workload runs on. If needed the CPUs can be forced using
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taskset.
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EXAMPLES
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--------
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$ perf stat -- make -j
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Performance counter stats for 'make -j':
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8117.370256 task clock ticks # 11.281 CPU utilization factor
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678 context switches # 0.000 M/sec
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133 CPU migrations # 0.000 M/sec
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235724 pagefaults # 0.029 M/sec
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24821162526 CPU cycles # 3057.784 M/sec
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18687303457 instructions # 2302.138 M/sec
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172158895 cache references # 21.209 M/sec
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27075259 cache misses # 3.335 M/sec
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Wall-clock time elapsed: 719.554352 msecs
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CSV FORMAT
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----------
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With -x, perf stat is able to output a not-quite-CSV format output
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Commas in the output are not put into "". To make it easy to parse
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it is recommended to use a different character like -x \;
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The fields are in this order:
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- optional usec time stamp in fractions of second (with -I xxx)
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- optional CPU, core, or socket identifier
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- optional number of logical CPUs aggregated
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- counter value
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- unit of the counter value or empty
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- event name
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- run time of counter
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- percentage of measurement time the counter was running
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- optional variance if multiple values are collected with -r
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- optional metric value
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- optional unit of metric
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Additional metrics may be printed with all earlier fields being empty.
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SEE ALSO
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--------
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linkperf:perf-top[1], linkperf:perf-list[1]
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