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diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt new file mode 100644 index 000000000..239af8f71 --- /dev/null +++ b/tools/perf/Documentation/perf-stat.txt @@ -0,0 +1,378 @@ +perf-stat(1) +============ + +NAME +---- +perf-stat - Run a command and gather performance counter statistics + +SYNOPSIS +-------- +[verse] +'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 symbolic or raw PMU event followed by an optional colon + and a list of event modifiers, e.g., cpu-cycles:p. See the + linkperf: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/* + + - 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 accross 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) + +-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. + +-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 + +--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' + +--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-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. + +-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 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. + +--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. + +EXAMPLES +-------- + +$ 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 +------- +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. + +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 +-------- +linkperf:perf-top[1], linkperf:perf-list[1] |