1perf-record(1)
2==============
3
4NAME
5----
6perf-record - Run a command and record its profile into perf.data
7
8SYNOPSIS
9--------
10[verse]
11'perf record' [-e <EVENT> | --event=EVENT] [-a] <command>
12'perf record' [-e <EVENT> | --event=EVENT] [-a] -- <command> [<options>]
13
14DESCRIPTION
15-----------
16This command runs a command and gathers a performance counter profile
17from it, into perf.data - without displaying anything.
18
19This file can then be inspected later on, using 'perf report'.
20
21
22OPTIONS
23-------
24<command>...::
25	Any command you can specify in a shell.
26
27-e::
28--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 is a
34	  hexadecimal event descriptor.
35
36        - a symbolic or raw PMU event followed by an optional colon
37	  and a list of event modifiers, e.g., cpu-cycles:p.  See the
38	  linkperf:perf-list[1] man page for details on event modifiers.
39
40	- a symbolically formed PMU event like 'pmu/param1=0x3,param2/' where
41	  'param1', 'param2', etc are defined as formats for the PMU in
42	  /sys/bus/event_source/devices/<pmu>/format/*.
43
44	- a symbolically formed event like 'pmu/config=M,config1=N,config3=K/'
45
46          where M, N, K are numbers (in decimal, hex, octal format). Acceptable
47          values for each of 'config', 'config1' and 'config2' are defined by
48          corresponding entries in /sys/bus/event_source/devices/<pmu>/format/*
49          param1 and param2 are defined as formats for the PMU in:
50          /sys/bus/event_source/devices/<pmu>/format/*
51
52	  There are also some parameters which are not defined in .../<pmu>/format/*.
53	  These params can be used to overload default config values per event.
54	  Here are some common parameters:
55	  - 'period': Set event sampling period
56	  - 'freq': Set event sampling frequency
57	  - 'time': Disable/enable time stamping. Acceptable values are 1 for
58		    enabling time stamping. 0 for disabling time stamping.
59		    The default is 1.
60	  - 'call-graph': Disable/enable callgraph. Acceptable str are "fp" for
61			 FP mode, "dwarf" for DWARF mode, "lbr" for LBR mode and
62			 "no" for disable callgraph.
63	  - 'stack-size': user stack size for dwarf mode
64	  - 'name' : User defined event name. Single quotes (') may be used to
65		    escape symbols in the name from parsing by shell and tool
66		    like this: name=\'CPU_CLK_UNHALTED.THREAD:cmask=0x1\'.
67	  - 'aux-output': Generate AUX records instead of events. This requires
68			  that an AUX area event is also provided.
69	  - 'aux-sample-size': Set sample size for AUX area sampling. If the
70	  '--aux-sample' option has been used, set aux-sample-size=0 to disable
71	  AUX area sampling for the event.
72
73          See the linkperf:perf-list[1] man page for more parameters.
74
75	  Note: If user explicitly sets options which conflict with the params,
76	  the value set by the parameters will be overridden.
77
78	  Also not defined in .../<pmu>/format/* are PMU driver specific
79	  configuration parameters.  Any configuration parameter preceded by
80	  the letter '@' is not interpreted in user space and sent down directly
81	  to the PMU driver.  For example:
82
83	  perf record -e some_event/@cfg1,@cfg2=config/ ...
84
85	  will see 'cfg1' and 'cfg2=config' pushed to the PMU driver associated
86	  with the event for further processing.  There is no restriction on
87	  what the configuration parameters are, as long as their semantic is
88	  understood and supported by the PMU driver.
89
90        - a hardware breakpoint event in the form of '\mem:addr[/len][:access]'
91          where addr is the address in memory you want to break in.
92          Access is the memory access type (read, write, execute) it can
93          be passed as follows: '\mem:addr[:[r][w][x]]'. len is the range,
94          number of bytes from specified addr, which the breakpoint will cover.
95          If you want to profile read-write accesses in 0x1000, just set
96          'mem:0x1000:rw'.
97          If you want to profile write accesses in [0x1000~1008), just set
98          'mem:0x1000/8:w'.
99
100        - a BPF source file (ending in .c) or a precompiled object file (ending
101          in .o) selects one or more BPF events.
102          The BPF program can attach to various perf events based on the ELF section
103          names.
104
105          When processing a '.c' file, perf searches an installed LLVM to compile it
106          into an object file first. Optional clang options can be passed via the
107          '--clang-opt' command line option, e.g.:
108
109            perf record --clang-opt "-DLINUX_VERSION_CODE=0x50000" \
110                        -e tests/bpf-script-example.c
111
112          Note: '--clang-opt' must be placed before '--event/-e'.
113
114	- a group of events surrounded by a pair of brace ("{event1,event2,...}").
115	  Each event is separated by commas and the group should be quoted to
116	  prevent the shell interpretation.  You also need to use --group on
117	  "perf report" to view group events together.
118
119--filter=<filter>::
120        Event filter. This option should follow an event selector (-e) which
121	selects either tracepoint event(s) or a hardware trace PMU
122	(e.g. Intel PT or CoreSight).
123
124	- tracepoint filters
125
126	In the case of tracepoints, multiple '--filter' options are combined
127	using '&&'.
128
129	- address filters
130
131	A hardware trace PMU advertises its ability to accept a number of
132	address filters	by specifying a non-zero value in
133	/sys/bus/event_source/devices/<pmu>/nr_addr_filters.
134
135	Address filters have the format:
136
137	filter|start|stop|tracestop <start> [/ <size>] [@<file name>]
138
139	Where:
140	- 'filter': defines a region that will be traced.
141	- 'start': defines an address at which tracing will begin.
142	- 'stop': defines an address at which tracing will stop.
143	- 'tracestop': defines a region in which tracing will stop.
144
145	<file name> is the name of the object file, <start> is the offset to the
146	code to trace in that file, and <size> is the size of the region to
147	trace. 'start' and 'stop' filters need not specify a <size>.
148
149	If no object file is specified then the kernel is assumed, in which case
150	the start address must be a current kernel memory address.
151
152	<start> can also be specified by providing the name of a symbol. If the
153	symbol name is not unique, it can be disambiguated by inserting #n where
154	'n' selects the n'th symbol in address order. Alternately #0, #g or #G
155	select only a global symbol. <size> can also be specified by providing
156	the name of a symbol, in which case the size is calculated to the end
157	of that symbol. For 'filter' and 'tracestop' filters, if <size> is
158	omitted and <start> is a symbol, then the size is calculated to the end
159	of that symbol.
160
161	If <size> is omitted and <start> is '*', then the start and size will
162	be calculated from the first and last symbols, i.e. to trace the whole
163	file.
164
165	If symbol names (or '*') are provided, they must be surrounded by white
166	space.
167
168	The filter passed to the kernel is not necessarily the same as entered.
169	To see the filter that is passed, use the -v option.
170
171	The kernel may not be able to configure a trace region if it is not
172	within a single mapping.  MMAP events (or /proc/<pid>/maps) can be
173	examined to determine if that is a possibility.
174
175	Multiple filters can be separated with space or comma.
176
177--exclude-perf::
178	Don't record events issued by perf itself. This option should follow
179	an event selector (-e) which selects tracepoint event(s). It adds a
180	filter expression 'common_pid != $PERFPID' to filters. If other
181	'--filter' exists, the new filter expression will be combined with
182	them by '&&'.
183
184-a::
185--all-cpus::
186        System-wide collection from all CPUs (default if no target is specified).
187
188-p::
189--pid=::
190	Record events on existing process ID (comma separated list).
191
192-t::
193--tid=::
194        Record events on existing thread ID (comma separated list).
195        This option also disables inheritance by default.  Enable it by adding
196        --inherit.
197
198-u::
199--uid=::
200        Record events in threads owned by uid. Name or number.
201
202-r::
203--realtime=::
204	Collect data with this RT SCHED_FIFO priority.
205
206--no-buffering::
207	Collect data without buffering.
208
209-c::
210--count=::
211	Event period to sample.
212
213-o::
214--output=::
215	Output file name.
216
217-i::
218--no-inherit::
219	Child tasks do not inherit counters.
220
221-F::
222--freq=::
223	Profile at this frequency. Use 'max' to use the currently maximum
224	allowed frequency, i.e. the value in the kernel.perf_event_max_sample_rate
225	sysctl. Will throttle down to the currently maximum allowed frequency.
226	See --strict-freq.
227
228--strict-freq::
229	Fail if the specified frequency can't be used.
230
231-m::
232--mmap-pages=::
233	Number of mmap data pages (must be a power of two) or size
234	specification with appended unit character - B/K/M/G. The
235	size is rounded up to have nearest pages power of two value.
236	Also, by adding a comma, the number of mmap pages for AUX
237	area tracing can be specified.
238
239--group::
240	Put all events in a single event group.  This precedes the --event
241	option and remains only for backward compatibility.  See --event.
242
243-g::
244	Enables call-graph (stack chain/backtrace) recording for both
245	kernel space and user space.
246
247--call-graph::
248	Setup and enable call-graph (stack chain/backtrace) recording,
249	implies -g.  Default is "fp" (for user space).
250
251	The unwinding method used for kernel space is dependent on the
252	unwinder used by the active kernel configuration, i.e
253	CONFIG_UNWINDER_FRAME_POINTER (fp) or CONFIG_UNWINDER_ORC (orc)
254
255	Any option specified here controls the method used for user space.
256
257	Valid options are "fp" (frame pointer), "dwarf" (DWARF's CFI -
258	Call Frame Information) or "lbr" (Hardware Last Branch Record
259	facility).
260
261	In some systems, where binaries are build with gcc
262	--fomit-frame-pointer, using the "fp" method will produce bogus
263	call graphs, using "dwarf", if available (perf tools linked to
264	the libunwind or libdw library) should be used instead.
265	Using the "lbr" method doesn't require any compiler options. It
266	will produce call graphs from the hardware LBR registers. The
267	main limitation is that it is only available on new Intel
268	platforms, such as Haswell. It can only get user call chain. It
269	doesn't work with branch stack sampling at the same time.
270
271	When "dwarf" recording is used, perf also records (user) stack dump
272	when sampled.  Default size of the stack dump is 8192 (bytes).
273	User can change the size by passing the size after comma like
274	"--call-graph dwarf,4096".
275
276-q::
277--quiet::
278	Don't print any message, useful for scripting.
279
280-v::
281--verbose::
282	Be more verbose (show counter open errors, etc).
283
284-s::
285--stat::
286	Record per-thread event counts.  Use it with 'perf report -T' to see
287	the values.
288
289-d::
290--data::
291	Record the sample virtual addresses.
292
293--phys-data::
294	Record the sample physical addresses.
295
296--data-page-size::
297	Record the sampled data address data page size.
298
299--code-page-size::
300	Record the sampled code address (ip) page size
301
302-T::
303--timestamp::
304	Record the sample timestamps. Use it with 'perf report -D' to see the
305	timestamps, for instance.
306
307-P::
308--period::
309	Record the sample period.
310
311--sample-cpu::
312	Record the sample cpu.
313
314-n::
315--no-samples::
316	Don't sample.
317
318-R::
319--raw-samples::
320Collect raw sample records from all opened counters (default for tracepoint counters).
321
322-C::
323--cpu::
324Collect samples only on the list of CPUs provided. Multiple CPUs can be provided as a
325comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2.
326In per-thread mode with inheritance mode on (default), samples are captured only when
327the thread executes on the designated CPUs. Default is to monitor all CPUs.
328
329-B::
330--no-buildid::
331Do not save the build ids of binaries in the perf.data files. This skips
332post processing after recording, which sometimes makes the final step in
333the recording process to take a long time, as it needs to process all
334events looking for mmap records. The downside is that it can misresolve
335symbols if the workload binaries used when recording get locally rebuilt
336or upgraded, because the only key available in this case is the
337pathname. You can also set the "record.build-id" config variable to
338'skip to have this behaviour permanently.
339
340-N::
341--no-buildid-cache::
342Do not update the buildid cache. This saves some overhead in situations
343where the information in the perf.data file (which includes buildids)
344is sufficient.  You can also set the "record.build-id" config variable to
345'no-cache' to have the same effect.
346
347-G name,...::
348--cgroup name,...::
349monitor only in the container (cgroup) called "name". This option is available only
350in per-cpu mode. The cgroup filesystem must be mounted. All threads belonging to
351container "name" are monitored when they run on the monitored CPUs. Multiple cgroups
352can be provided. Each cgroup is applied to the corresponding event, i.e., first cgroup
353to first event, second cgroup to second event and so on. It is possible to provide
354an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have
355corresponding events, i.e., they always refer to events defined earlier on the command
356line. If the user wants to track multiple events for a specific cgroup, the user can
357use '-e e1 -e e2 -G foo,foo' or just use '-e e1 -e e2 -G foo'.
358
359If wanting to monitor, say, 'cycles' for a cgroup and also for system wide, this
360command line can be used: 'perf stat -e cycles -G cgroup_name -a -e cycles'.
361
362-b::
363--branch-any::
364Enable taken branch stack sampling. Any type of taken branch may be sampled.
365This is a shortcut for --branch-filter any. See --branch-filter for more infos.
366
367-j::
368--branch-filter::
369Enable taken branch stack sampling. Each sample captures a series of consecutive
370taken branches. The number of branches captured with each sample depends on the
371underlying hardware, the type of branches of interest, and the executed code.
372It is possible to select the types of branches captured by enabling filters. The
373following filters are defined:
374
375        - any:  any type of branches
376        - any_call: any function call or system call
377        - any_ret: any function return or system call return
378        - ind_call: any indirect branch
379        - call: direct calls, including far (to/from kernel) calls
380        - u:  only when the branch target is at the user level
381        - k: only when the branch target is in the kernel
382        - hv: only when the target is at the hypervisor level
383	- in_tx: only when the target is in a hardware transaction
384	- no_tx: only when the target is not in a hardware transaction
385	- abort_tx: only when the target is a hardware transaction abort
386	- cond: conditional branches
387	- save_type: save branch type during sampling in case binary is not available later
388
389+
390The option requires at least one branch type among any, any_call, any_ret, ind_call, cond.
391The privilege levels may be omitted, in which case, the privilege levels of the associated
392event are applied to the branch filter. Both kernel (k) and hypervisor (hv) privilege
393levels are subject to permissions.  When sampling on multiple events, branch stack sampling
394is enabled for all the sampling events. The sampled branch type is the same for all events.
395The various filters must be specified as a comma separated list: --branch-filter any_ret,u,k
396Note that this feature may not be available on all processors.
397
398--weight::
399Enable weightened sampling. An additional weight is recorded per sample and can be
400displayed with the weight and local_weight sort keys.  This currently works for TSX
401abort events and some memory events in precise mode on modern Intel CPUs.
402
403--namespaces::
404Record events of type PERF_RECORD_NAMESPACES.  This enables 'cgroup_id' sort key.
405
406--all-cgroups::
407Record events of type PERF_RECORD_CGROUP.  This enables 'cgroup' sort key.
408
409--transaction::
410Record transaction flags for transaction related events.
411
412--per-thread::
413Use per-thread mmaps.  By default per-cpu mmaps are created.  This option
414overrides that and uses per-thread mmaps.  A side-effect of that is that
415inheritance is automatically disabled.  --per-thread is ignored with a warning
416if combined with -a or -C options.
417
418-D::
419--delay=::
420After starting the program, wait msecs before measuring (-1: start with events
421disabled). This is useful to filter out the startup phase of the program, which
422is often very different.
423
424-I::
425--intr-regs::
426Capture machine state (registers) at interrupt, i.e., on counter overflows for
427each sample. List of captured registers depends on the architecture. This option
428is off by default. It is possible to select the registers to sample using their
429symbolic names, e.g. on x86, ax, si. To list the available registers use
430--intr-regs=\?. To name registers, pass a comma separated list such as
431--intr-regs=ax,bx. The list of register is architecture dependent.
432
433--user-regs::
434Similar to -I, but capture user registers at sample time. To list the available
435user registers use --user-regs=\?.
436
437--running-time::
438Record running and enabled time for read events (:S)
439
440-k::
441--clockid::
442Sets the clock id to use for the various time fields in the perf_event_type
443records. See clock_gettime(). In particular CLOCK_MONOTONIC and
444CLOCK_MONOTONIC_RAW are supported, some events might also allow
445CLOCK_BOOTTIME, CLOCK_REALTIME and CLOCK_TAI.
446
447-S::
448--snapshot::
449Select AUX area tracing Snapshot Mode. This option is valid only with an
450AUX area tracing event. Optionally, certain snapshot capturing parameters
451can be specified in a string that follows this option:
452  'e': take one last snapshot on exit; guarantees that there is at least one
453       snapshot in the output file;
454  <size>: if the PMU supports this, specify the desired snapshot size.
455
456In Snapshot Mode trace data is captured only when signal SIGUSR2 is received
457and on exit if the above 'e' option is given.
458
459--aux-sample[=OPTIONS]::
460Select AUX area sampling. At least one of the events selected by the -e option
461must be an AUX area event. Samples on other events will be created containing
462data from the AUX area. Optionally sample size may be specified, otherwise it
463defaults to 4KiB.
464
465--proc-map-timeout::
466When processing pre-existing threads /proc/XXX/mmap, it may take a long time,
467because the file may be huge. A time out is needed in such cases.
468This option sets the time out limit. The default value is 500 ms.
469
470--switch-events::
471Record context switch events i.e. events of type PERF_RECORD_SWITCH or
472PERF_RECORD_SWITCH_CPU_WIDE. In some cases (e.g. Intel PT or CoreSight)
473switch events will be enabled automatically, which can be suppressed by
474by the option --no-switch-events.
475
476--clang-path=PATH::
477Path to clang binary to use for compiling BPF scriptlets.
478(enabled when BPF support is on)
479
480--clang-opt=OPTIONS::
481Options passed to clang when compiling BPF scriptlets.
482(enabled when BPF support is on)
483
484--vmlinux=PATH::
485Specify vmlinux path which has debuginfo.
486(enabled when BPF prologue is on)
487
488--buildid-all::
489Record build-id of all DSOs regardless whether it's actually hit or not.
490
491--buildid-mmap::
492Record build ids in mmap2 events, disables build id cache (implies --no-buildid).
493
494--aio[=n]::
495Use <n> control blocks in asynchronous (Posix AIO) trace writing mode (default: 1, max: 4).
496Asynchronous mode is supported only when linking Perf tool with libc library
497providing implementation for Posix AIO API.
498
499--affinity=mode::
500Set affinity mask of trace reading thread according to the policy defined by 'mode' value:
501  node - thread affinity mask is set to NUMA node cpu mask of the processed mmap buffer
502  cpu  - thread affinity mask is set to cpu of the processed mmap buffer
503
504--mmap-flush=number::
505
506Specify minimal number of bytes that is extracted from mmap data pages and
507processed for output. One can specify the number using B/K/M/G suffixes.
508
509The maximal allowed value is a quarter of the size of mmaped data pages.
510
511The default option value is 1 byte which means that every time that the output
512writing thread finds some new data in the mmaped buffer the data is extracted,
513possibly compressed (-z) and written to the output, perf.data or pipe.
514
515Larger data chunks are compressed more effectively in comparison to smaller
516chunks so extraction of larger chunks from the mmap data pages is preferable
517from the perspective of output size reduction.
518
519Also at some cases executing less output write syscalls with bigger data size
520can take less time than executing more output write syscalls with smaller data
521size thus lowering runtime profiling overhead.
522
523-z::
524--compression-level[=n]::
525Produce compressed trace using specified level n (default: 1 - fastest compression,
52622 - smallest trace)
527
528--all-kernel::
529Configure all used events to run in kernel space.
530
531--all-user::
532Configure all used events to run in user space.
533
534--kernel-callchains::
535Collect callchains only from kernel space. I.e. this option sets
536perf_event_attr.exclude_callchain_user to 1.
537
538--user-callchains::
539Collect callchains only from user space. I.e. this option sets
540perf_event_attr.exclude_callchain_kernel to 1.
541
542Don't use both --kernel-callchains and --user-callchains at the same time or no
543callchains will be collected.
544
545--timestamp-filename
546Append timestamp to output file name.
547
548--timestamp-boundary::
549Record timestamp boundary (time of first/last samples).
550
551--switch-output[=mode]::
552Generate multiple perf.data files, timestamp prefixed, switching to a new one
553based on 'mode' value:
554  "signal" - when receiving a SIGUSR2 (default value) or
555  <size>   - when reaching the size threshold, size is expected to
556             be a number with appended unit character - B/K/M/G
557  <time>   - when reaching the time threshold, size is expected to
558             be a number with appended unit character - s/m/h/d
559
560             Note: the precision of  the size  threshold  hugely depends
561             on your configuration  - the number and size of  your  ring
562             buffers (-m). It is generally more precise for higher sizes
563             (like >5M), for lower values expect different sizes.
564
565A possible use case is to, given an external event, slice the perf.data file
566that gets then processed, possibly via a perf script, to decide if that
567particular perf.data snapshot should be kept or not.
568
569Implies --timestamp-filename, --no-buildid and --no-buildid-cache.
570The reason for the latter two is to reduce the data file switching
571overhead. You can still switch them on with:
572
573  --switch-output --no-no-buildid  --no-no-buildid-cache
574
575--switch-output-event::
576Events that will cause the switch of the perf.data file, auto-selecting
577--switch-output=signal, the results are similar as internally the side band
578thread will also send a SIGUSR2 to the main one.
579
580Uses the same syntax as --event, it will just not be recorded, serving only to
581switch the perf.data file as soon as the --switch-output event is processed by
582a separate sideband thread.
583
584This sideband thread is also used to other purposes, like processing the
585PERF_RECORD_BPF_EVENT records as they happen, asking the kernel for extra BPF
586information, etc.
587
588--switch-max-files=N::
589
590When rotating perf.data with --switch-output, only keep N files.
591
592--dry-run::
593Parse options then exit. --dry-run can be used to detect errors in cmdline
594options.
595
596'perf record --dry-run -e' can act as a BPF script compiler if llvm.dump-obj
597in config file is set to true.
598
599--tail-synthesize::
600Instead of collecting non-sample events (for example, fork, comm, mmap) at
601the beginning of record, collect them during finalizing an output file.
602The collected non-sample events reflects the status of the system when
603record is finished.
604
605--overwrite::
606Makes all events use an overwritable ring buffer. An overwritable ring
607buffer works like a flight recorder: when it gets full, the kernel will
608overwrite the oldest records, that thus will never make it to the
609perf.data file.
610
611When '--overwrite' and '--switch-output' are used perf records and drops
612events until it receives a signal, meaning that something unusual was
613detected that warrants taking a snapshot of the most current events,
614those fitting in the ring buffer at that moment.
615
616'overwrite' attribute can also be set or canceled for an event using
617config terms. For example: 'cycles/overwrite/' and 'instructions/no-overwrite/'.
618
619Implies --tail-synthesize.
620
621--kcore::
622Make a copy of /proc/kcore and place it into a directory with the perf data file.
623
624--max-size=<size>::
625Limit the sample data max size, <size> is expected to be a number with
626appended unit character - B/K/M/G
627
628--num-thread-synthesize::
629	The number of threads to run when synthesizing events for existing processes.
630	By default, the number of threads equals 1.
631
632ifdef::HAVE_LIBPFM[]
633--pfm-events events::
634Select a PMU event using libpfm4 syntax (see http://perfmon2.sf.net)
635including support for event filters. For example '--pfm-events
636inst_retired:any_p:u:c=1:i'. More than one event can be passed to the
637option using the comma separator. Hardware events and generic hardware
638events cannot be mixed together. The latter must be used with the -e
639option. The -e option and this one can be mixed and matched.  Events
640can be grouped using the {} notation.
641endif::HAVE_LIBPFM[]
642
643--control=fifo:ctl-fifo[,ack-fifo]::
644--control=fd:ctl-fd[,ack-fd]::
645ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as follows.
646Listen on ctl-fd descriptor for command to control measurement.
647
648Available commands:
649  'enable'           : enable events
650  'disable'          : disable events
651  'enable name'      : enable event 'name'
652  'disable name'     : disable event 'name'
653  'snapshot'         : AUX area tracing snapshot).
654  'stop'             : stop perf record
655  'ping'             : ping
656
657  'evlist [-v|-g|-F] : display all events
658                       -F  Show just the sample frequency used for each event.
659                       -v  Show all fields.
660                       -g  Show event group information.
661
662Measurements can be started with events disabled using --delay=-1 option. Optionally
663send control command completion ('ack\n') to ack-fd descriptor to synchronize with the
664controlling process.  Example of bash shell script to enable and disable events during
665measurements:
666
667 #!/bin/bash
668
669 ctl_dir=/tmp/
670
671 ctl_fifo=${ctl_dir}perf_ctl.fifo
672 test -p ${ctl_fifo} && unlink ${ctl_fifo}
673 mkfifo ${ctl_fifo}
674 exec {ctl_fd}<>${ctl_fifo}
675
676 ctl_ack_fifo=${ctl_dir}perf_ctl_ack.fifo
677 test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo}
678 mkfifo ${ctl_ack_fifo}
679 exec {ctl_fd_ack}<>${ctl_ack_fifo}
680
681 perf record -D -1 -e cpu-cycles -a               \
682             --control fd:${ctl_fd},${ctl_fd_ack} \
683             -- sleep 30 &
684 perf_pid=$!
685
686 sleep 5  && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})"
687 sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})"
688
689 exec {ctl_fd_ack}>&-
690 unlink ${ctl_ack_fifo}
691
692 exec {ctl_fd}>&-
693 unlink ${ctl_fifo}
694
695 wait -n ${perf_pid}
696 exit $?
697
698
699SEE ALSO
700--------
701linkperf:perf-stat[1], linkperf:perf-list[1], linkperf:perf-intel-pt[1]
702