1PERF-STAT(1)                      perf Manual                     PERF-STAT(1)
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NAME

6       perf-stat - Run a command and gather performance counter statistics
7

SYNOPSIS

9       perf stat [-e <EVENT> | --event=EVENT] [-a] <command>
10       perf stat [-e <EVENT> | --event=EVENT] [-a] — <command> [<options>]
11       perf stat [-e <EVENT> | --event=EVENT] [-a] record [-o file] — <command> [<options>]
12       perf stat report [-i file]
13

DESCRIPTION

15       This command runs a command and gathers performance counter statistics
16       from it.
17

OPTIONS

19       <command>...
20           Any command you can specify in a shell.
21
22       record
23           See STAT RECORD.
24
25       report
26           See STAT REPORT.
27
28       -e, --event=
29           Select the PMU event. Selection can be:
30
31           ·   a symbolic event name (use perf list to list all events)
32
33           ·   a raw PMU event (eventsel+umask) in the form of rNNN where NNN
34               is a hexadecimal event descriptor.
35
36           ·   a symbolically formed event like pmu/param1=0x3,param2/ where
37               param1 and param2 are defined as formats for the PMU in
38               /sys/bus/event_source/devices/<pmu>/format/*
39
40           ·   a symbolically formed event like
41               pmu/config=M,config1=N,config2=K/ where M, N, K are numbers (in
42               decimal, hex, octal format). Acceptable values for each of
43               config, config1 and config2 parameters are defined by
44               corresponding entries in
45               /sys/bus/event_source/devices/<pmu>/format/*
46
47                   Note that the last two syntaxes support prefix and glob matching in
48                   the PMU name to simplify creation of events across multiple instances
49                   of the same type of PMU in large systems (e.g. memory controller PMUs).
50                   Multiple PMU instances are typical for uncore PMUs, so the prefix
51                   'uncore_' is also ignored when performing this match.
52
53       -i, --no-inherit
54           child tasks do not inherit counters
55
56       -p, --pid=<pid>
57           stat events on existing process id (comma separated list)
58
59       -t, --tid=<tid>
60           stat events on existing thread id (comma separated list)
61
62       -a, --all-cpus
63           system-wide collection from all CPUs (default if no target is
64           specified)
65
66       --no-scale
67           Don’t scale/normalize counter values
68
69       -d, --detailed
70           print more detailed statistics, can be specified up to 3 times
71
72                     -d:          detailed events, L1 and LLC data cache
73                  -d -d:     more detailed events, dTLB and iTLB events
74               -d -d -d:     very detailed events, adding prefetch events
75
76       -r, --repeat=<n>
77           repeat command and print average + stddev (max: 100). 0 means
78           forever.
79
80       -B, --big-num
81           print large numbers with thousands' separators according to locale
82
83       -C, --cpu=
84           Count only on the list of CPUs provided. Multiple CPUs can be
85           provided as a comma-separated list with no space: 0,1. Ranges of
86           CPUs are specified with -: 0-2. In per-thread mode, this option is
87           ignored. The -a option is still necessary to activate system-wide
88           monitoring. Default is to count on all CPUs.
89
90       -A, --no-aggr
91           Do not aggregate counts across all monitored CPUs.
92
93       -n, --null
94           null run - don’t start any counters
95
96       -v, --verbose
97           be more verbose (show counter open errors, etc)
98
99       -x SEP, --field-separator SEP
100           print counts using a CSV-style output to make it easy to import
101           directly into spreadsheets. Columns are separated by the string
102           specified in SEP.
103
104       --table
105           Display time for each run (-r option), in a table format, e.g.:
106
107               $ perf stat --null -r 5 --table perf bench sched pipe
108
109               Performance counter stats for 'perf bench sched pipe' (5 runs):
110
111               # Table of individual measurements:
112               5.189 (-0.293) #
113               5.189 (-0.294) #
114               5.186 (-0.296) #
115               5.663 (+0.181) ##
116               6.186 (+0.703) ####
117
118               # Final result:
119               5.483 +- 0.198 seconds time elapsed  ( +-  3.62% )
120
121       -G name, --cgroup name
122           monitor only in the container (cgroup) called "name". This option
123           is available only in per-cpu mode. The cgroup filesystem must be
124           mounted. All threads belonging to container "name" are monitored
125           when they run on the monitored CPUs. Multiple cgroups can be
126           provided. Each cgroup is applied to the corresponding event, i.e.,
127           first cgroup to first event, second cgroup to second event and so
128           on. It is possible to provide an empty cgroup (monitor all the
129           time) using, e.g., -G foo,,bar. Cgroups must have corresponding
130           events, i.e., they always refer to events defined earlier on the
131           command line. If the user wants to track multiple events for a
132           specific cgroup, the user can use -e e1 -e e2 -G foo,foo or just
133           use -e e1 -e e2 -G foo.
134
135       If wanting to monitor, say, cycles for a cgroup and also for system
136       wide, this command line can be used: perf stat -e cycles -G cgroup_name
137       -a -e cycles.
138
139       -o file, --output file
140           Print the output into the designated file.
141
142       --append
143           Append to the output file designated with the -o option. Ignored if
144           -o is not specified.
145
146       --log-fd
147           Log output to fd, instead of stderr. Complementary to --output, and
148           mutually exclusive with it. --append may be used here. Examples:
149           3>results perf stat --log-fd 3  — $cmd 3>>results perf stat
150           --log-fd 3 --append — $cmd
151
152       --pre, --post
153           Pre and post measurement hooks, e.g.:
154
155       perf stat --repeat 10 --null --sync --pre make -s
156       O=defconfig-build/clean — make -s -j64 O=defconfig-build/ bzImage
157
158       -I msecs, --interval-print msecs
159           Print count deltas every N milliseconds (minimum: 1ms) The overhead
160           percentage could be high in some cases, for instance with small,
161           sub 100ms intervals. Use with caution. example: perf stat -I 1000
162           -e cycles -a sleep 5
163
164       --interval-count times
165           Print count deltas for fixed number of times. This option should be
166           used together with "-I" option. example: perf stat -I 1000
167           --interval-count 2 -e cycles -a
168
169       --interval-clear
170           Clear the screen before next interval.
171
172       --timeout msecs
173           Stop the perf stat session and print count deltas after N
174           milliseconds (minimum: 10 ms). This option is not supported with
175           the "-I" option. example: perf stat --time 2000 -e cycles -a
176
177       --metric-only
178           Only print computed metrics. Print them in a single line. Don’t
179           show any raw values. Not supported with --per-thread.
180
181       --per-socket
182           Aggregate counts per processor socket for system-wide mode
183           measurements. This is a useful mode to detect imbalance between
184           sockets. To enable this mode, use --per-socket in addition to -a.
185           (system-wide). The output includes the socket number and the number
186           of online processors on that socket. This is useful to gauge the
187           amount of aggregation.
188
189       --per-core
190           Aggregate counts per physical processor for system-wide mode
191           measurements. This is a useful mode to detect imbalance between
192           physical cores. To enable this mode, use --per-core in addition to
193           -a. (system-wide). The output includes the core number and the
194           number of online logical processors on that physical processor.
195
196       --per-thread
197           Aggregate counts per monitored threads, when monitoring threads (-t
198           option) or processes (-p option).
199
200       -D msecs, --delay msecs
201           After starting the program, wait msecs before measuring. This is
202           useful to filter out the startup phase of the program, which is
203           often very different.
204
205       -T, --transaction
206           Print statistics of transactional execution if supported.
207

STAT RECORD

209       Stores stat data into perf data file.
210
211       -o file, --output file
212           Output file name.
213

STAT REPORT

215       Reads and reports stat data from perf data file.
216
217       -i file, --input file
218           Input file name.
219
220       --per-socket
221           Aggregate counts per processor socket for system-wide mode
222           measurements.
223
224       --per-core
225           Aggregate counts per physical processor for system-wide mode
226           measurements.
227
228       -M, --metrics
229           Print metrics or metricgroups specified in a comma separated list.
230           For a group all metrics from the group are added. The events from
231           the metrics are automatically measured. See perf list output for
232           the possble metrics and metricgroups.
233
234       -A, --no-aggr
235           Do not aggregate counts across all monitored CPUs.
236
237       --topdown
238           Print top down level 1 metrics if supported by the CPU. This allows
239           to determine bottle necks in the CPU pipeline for CPU bound
240           workloads, by breaking the cycles consumed down into frontend
241           bound, backend bound, bad speculation and retiring.
242
243       Frontend bound means that the CPU cannot fetch and decode instructions
244       fast enough. Backend bound means that computation or memory access is
245       the bottle neck. Bad Speculation means that the CPU wasted cycles due
246       to branch mispredictions and similar issues. Retiring means that the
247       CPU computed without an apparently bottleneck. The bottleneck is only
248       the real bottleneck if the workload is actually bound by the CPU and
249       not by something else.
250
251       For best results it is usually a good idea to use it with interval mode
252       like -I 1000, as the bottleneck of workloads can change often.
253
254       The top down metrics are collected per core instead of per CPU thread.
255       Per core mode is automatically enabled and -a (global monitoring) is
256       needed, requiring root rights or perf.perf_event_paranoid=-1.
257
258       Topdown uses the full Performance Monitoring Unit, and needs disabling
259       of the NMI watchdog (as root): echo 0 > /proc/sys/kernel/nmi_watchdog
260       for best results. Otherwise the bottlenecks may be inconsistent on
261       workload with changing phases.
262
263       This enables --metric-only, unless overridden with --no-metric-only.
264
265       To interpret the results it is usually needed to know on which CPUs the
266       workload runs on. If needed the CPUs can be forced using taskset.
267
268       --no-merge
269           Do not merge results from same PMUs.
270
271       When multiple events are created from a single event specification,
272       stat will, by default, aggregate the event counts and show the result
273       in a single row. This option disables that behavior and shows the
274       individual events and counts.
275
276       Multiple events are created from a single event specification when: 1.
277       Prefix or glob matching is used for the PMU name. 2. Aliases, which are
278       listed immediately after the Kernel PMU events by perf list, are used.
279
280       --smi-cost
281           Measure SMI cost if msr/aperf/ and msr/smi/ events are supported.
282
283       During the measurement, the /sys/device/cpu/freeze_on_smi will be set
284       to freeze core counters on SMI. The aperf counter will not be effected
285       by the setting. The cost of SMI can be measured by (aperf - unhalted
286       core cycles).
287
288       In practice, the percentages of SMI cycles is very useful for
289       performance oriented analysis. --metric_only will be applied by
290       default. The output is SMI cycles%, equals to (aperf - unhalted core
291       cycles) / aperf
292
293       Users who wants to get the actual value can apply --no-metric-only.
294

EXAMPLES

296       $ perf stat — make
297
298           Performance counter stats for 'make':
299
300              83723.452481      task-clock:u (msec)       #    1.004 CPUs utilized
301                         0      context-switches:u        #    0.000 K/sec
302                         0      cpu-migrations:u          #    0.000 K/sec
303                 3,228,188      page-faults:u             #    0.039 M/sec
304           229,570,665,834      cycles:u                  #    2.742 GHz
305           313,163,853,778      instructions:u            #    1.36  insn per cycle
306            69,704,684,856      branches:u                #  832.559 M/sec
307             2,078,861,393      branch-misses:u           #    2.98% of all branches
308
309           83.409183620 seconds time elapsed
310
311           74.684747000 seconds user
312            8.739217000 seconds sys
313

TIMINGS

315       As displayed in the example above we can display 3 types of timings. We
316       always display the time the counters were enabled/alive:
317
318           83.409183620 seconds time elapsed
319
320       For workload sessions we also display time the workloads spent in
321       user/system lands:
322
323           74.684747000 seconds user
324            8.739217000 seconds sys
325
326       Those times are the very same as displayed by the time tool.
327

CSV FORMAT

329       With -x, perf stat is able to output a not-quite-CSV format output
330       Commas in the output are not put into "". To make it easy to parse it
331       is recommended to use a different character like -x \;
332
333       The fields are in this order:
334
335       ·   optional usec time stamp in fractions of second (with -I xxx)
336
337       ·   optional CPU, core, or socket identifier
338
339       ·   optional number of logical CPUs aggregated
340
341       ·   counter value
342
343       ·   unit of the counter value or empty
344
345       ·   event name
346
347       ·   run time of counter
348
349       ·   percentage of measurement time the counter was running
350
351       ·   optional variance if multiple values are collected with -r
352
353       ·   optional metric value
354
355       ·   optional unit of metric
356
357       Additional metrics may be printed with all earlier fields being empty.
358

SEE ALSO

360       perf-top(1), perf-list(1)
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364perf                              06/03/2019                      PERF-STAT(1)
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