perf-record(1) — Linux manual page


PERF-RECORD(1)                   perf Manual                  PERF-RECORD(1)

NAME         top

       perf-record - Run a command and record its profile into

SYNOPSIS         top

       perf record [-e <EVENT> | --event=EVENT] [-a] <command>
       perf record [-e <EVENT> | --event=EVENT] [-a] — <command> [<options>]

DESCRIPTION         top

       This command runs a command and gathers a performance counter profile
       from it, into - without displaying anything.

       This file can then be inspected later on, using perf report.

OPTIONS         top

           Any command you can specify in a shell.

       -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
               perf-list(1) man page for details on event modifiers.

           •   a symbolically formed PMU event like pmu/param1=0x3,param2/
               where param1, param2, etc are defined as formats for the PMU
               in /sys/bus/event_source/devices/<pmu>/format/*.

           •   a symbolically formed event like

                   where M, N, K are numbers (in decimal, hex, octal format). Acceptable
                   values for each of 'config', 'config1' and 'config2' are defined by
                   corresponding entries in /sys/bus/event_source/devices/<pmu>/format/*
                   param1 and param2 are defined as formats for the PMU in:

                   There are also some parameters which are not defined in .../<pmu>/format/*.
                   These params can be used to overload default config values per event.
                   Here are some common parameters:
                   - 'period': Set event sampling period
                   - 'freq': Set event sampling frequency
                   - 'time': Disable/enable time stamping. Acceptable values are 1 for
                             enabling time stamping. 0 for disabling time stamping.
                             The default is 1.
                   - 'call-graph': Disable/enable callgraph. Acceptable str are "fp" for
                                  FP mode, "dwarf" for DWARF mode, "lbr" for LBR mode and
                                  "no" for disable callgraph.
                   - 'stack-size': user stack size for dwarf mode
                   - 'name' : User defined event name. Single quotes (') may be used to
                             escape symbols in the name from parsing by shell and tool
                             like this: name=\'CPU_CLK_UNHALTED.THREAD:cmask=0x1\'.
                   - 'aux-output': Generate AUX records instead of events. This requires
                                   that an AUX area event is also provided.
                   - 'aux-sample-size': Set sample size for AUX area sampling. If the
                   '--aux-sample' option has been used, set aux-sample-size=0 to disable
                   AUX area sampling for the event.

                   See the linkperf:perf-list[1] man page for more parameters.

                   Note: If user explicitly sets options which conflict with the params,
                   the value set by the parameters will be overridden.

                   Also not defined in .../<pmu>/format/* are PMU driver specific
                   configuration parameters.  Any configuration parameter preceded by
                   the letter '@' is not interpreted in user space and sent down directly
                   to the PMU driver.  For example:

                   perf record -e some_event/@cfg1,@cfg2=config/ ...

                   will see 'cfg1' and 'cfg2=config' pushed to the PMU driver associated
                   with the event for further processing.  There is no restriction on
                   what the configuration parameters are, as long as their semantic is
                   understood and supported by the PMU driver.

           •   a hardware breakpoint event in the form of
               \mem:addr[/len][:access] where addr is the address in memory
               you want to break in. Access is the memory access type (read,
               write, execute) it can be passed as follows:
               \mem:addr[:[r][w][x]]. len is the range, number of bytes from
               specified addr, which the breakpoint will cover. If you want
               to profile read-write accesses in 0x1000, just set
               mem:0x1000:rw. If you want to profile write accesses in
               [0x1000~1008), just set mem:0x1000/8:w.

           •   a BPF source file (ending in .c) or a precompiled object file
               (ending in .o) selects one or more BPF events. The BPF
               program can attach to various perf events based on the ELF
               section names.

                   When processing a '.c' file, perf searches an installed LLVM to compile it
                   into an object file first. Optional clang options can be passed via the
                   '--clang-opt' command line option, e.g.:

                   perf record --clang-opt "-DLINUX_VERSION_CODE=0x50000" \
                               -e tests/bpf-script-example.c

                   Note: '--clang-opt' must be placed before '--event/-e'.

           •   a group of events surrounded by a pair of brace
               ("{event1,event2,...}"). Each event is separated by commas
               and the group should be quoted to prevent the shell
               interpretation. You also need to use --group on "perf report"
               to view group events together.

           Event filter. This option should follow an event selector (-e)
           which selects either tracepoint event(s) or a hardware trace PMU
           (e.g. Intel PT or CoreSight).

           •   tracepoint filters

                   In the case of tracepoints, multiple '--filter' options are combined
                   using '&&'.

           •   address filters

                   A hardware trace PMU advertises its ability to accept a number of
                   address filters by specifying a non-zero value in

                   Address filters have the format:

                   filter|start|stop|tracestop <start> [/ <size>] [@<file name>]

                   - 'filter': defines a region that will be traced.
                   - 'start': defines an address at which tracing will begin.
                   - 'stop': defines an address at which tracing will stop.
                   - 'tracestop': defines a region in which tracing will stop.

                   <file name> is the name of the object file, <start> is the offset to the
                   code to trace in that file, and <size> is the size of the region to
                   trace. 'start' and 'stop' filters need not specify a <size>.

                   If no object file is specified then the kernel is assumed, in which case
                   the start address must be a current kernel memory address.

                   <start> can also be specified by providing the name of a symbol. If the
                   symbol name is not unique, it can be disambiguated by inserting #n where
                   'n' selects the n'th symbol in address order. Alternately #0, #g or #G
                   select only a global symbol. <size> can also be specified by providing
                   the name of a symbol, in which case the size is calculated to the end
                   of that symbol. For 'filter' and 'tracestop' filters, if <size> is
                   omitted and <start> is a symbol, then the size is calculated to the end
                   of that symbol.

                   If <size> is omitted and <start> is '*', then the start and size will
                   be calculated from the first and last symbols, i.e. to trace the whole

                   If symbol names (or '*') are provided, they must be surrounded by white

                   The filter passed to the kernel is not necessarily the same as entered.
                   To see the filter that is passed, use the -v option.

                   The kernel may not be able to configure a trace region if it is not
                   within a single mapping.  MMAP events (or /proc/<pid>/maps) can be
                   examined to determine if that is a possibility.

                   Multiple filters can be separated with space or comma.

           Don’t record events issued by perf itself. This option should
           follow an event selector (-e) which selects tracepoint event(s).
           It adds a filter expression common_pid != $PERFPID to filters. If
           other --filter exists, the new filter expression will be combined
           with them by &&.

       -a, --all-cpus
           System-wide collection from all CPUs (default if no target is

       -p, --pid=
           Record events on existing process ID (comma separated list).

       -t, --tid=
           Record events on existing thread ID (comma separated list). This
           option also disables inheritance by default. Enable it by adding

       -u, --uid=
           Record events in threads owned by uid. Name or number.

       -r, --realtime=
           Collect data with this RT SCHED_FIFO priority.

           Collect data without buffering.

       -c, --count=
           Event period to sample.

       -o, --output=
           Output file name.

       -i, --no-inherit
           Child tasks do not inherit counters.

       -F, --freq=
           Profile at this frequency. Use max to use the currently maximum
           allowed frequency, i.e. the value in the
           kernel.perf_event_max_sample_rate sysctl. Will throttle down to
           the currently maximum allowed frequency. See --strict-freq.

           Fail if the specified frequency can’t be used.

       -m, --mmap-pages=
           Number of mmap data pages (must be a power of two) or size
           specification with appended unit character - B/K/M/G. The size is
           rounded up to have nearest pages power of two value. Also, by
           adding a comma, the number of mmap pages for AUX area tracing can
           be specified.

           Put all events in a single event group. This precedes the --event
           option and remains only for backward compatibility. See --event.

           Enables call-graph (stack chain/backtrace) recording for both
           kernel space and user space.

           Setup and enable call-graph (stack chain/backtrace) recording,
           implies -g. Default is "fp" (for user space).

               The unwinding method used for kernel space is dependent on the
               unwinder used by the active kernel configuration, i.e

               Any option specified here controls the method used for user space.

               Valid options are "fp" (frame pointer), "dwarf" (DWARF's CFI -
               Call Frame Information) or "lbr" (Hardware Last Branch Record

               In some systems, where binaries are build with gcc
               --fomit-frame-pointer, using the "fp" method will produce bogus
               call graphs, using "dwarf", if available (perf tools linked to
               the libunwind or libdw library) should be used instead.
               Using the "lbr" method doesn't require any compiler options. It
               will produce call graphs from the hardware LBR registers. The
               main limitation is that it is only available on new Intel
               platforms, such as Haswell. It can only get user call chain. It
               doesn't work with branch stack sampling at the same time.

               When "dwarf" recording is used, perf also records (user) stack dump
               when sampled.  Default size of the stack dump is 8192 (bytes).
               User can change the size by passing the size after comma like
               "--call-graph dwarf,4096".

       -q, --quiet
           Don’t print any message, useful for scripting.

       -v, --verbose
           Be more verbose (show counter open errors, etc).

       -s, --stat
           Record per-thread event counts. Use it with perf report -T to see
           the values.

       -d, --data
           Record the sample virtual addresses.

           Record the sample physical addresses.

       -T, --timestamp
           Record the sample timestamps. Use it with perf report -D to see
           the timestamps, for instance.

       -P, --period
           Record the sample period.

           Record the sample cpu.

       -n, --no-samples
           Don’t sample.

       -R, --raw-samples
           Collect raw sample records from all opened counters (default for
           tracepoint counters).

       -C, --cpu
           Collect samples 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 with
           inheritance mode on (default), samples are captured only when the
           thread executes on the designated CPUs. Default is to monitor all

       -B, --no-buildid
           Do not save the build ids of binaries in the files.
           This skips post processing after recording, which sometimes makes
           the final step in the recording process to take a long time, as
           it needs to process all events looking for mmap records. The
           downside is that it can misresolve symbols if the workload
           binaries used when recording get locally rebuilt or upgraded,
           because the only key available in this case is the pathname. You
           can also set the "" config variable to 'skip to
           have this behaviour permanently.

       -N, --no-buildid-cache
           Do not update the buildid cache. This saves some overhead in
           situations where the information in the file (which
           includes buildids) is sufficient. You can also set the
           "" config variable to no-cache to have the same

       -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.

       -b, --branch-any
           Enable taken branch stack sampling. Any type of taken branch may
           be sampled. This is a shortcut for --branch-filter any. See
           --branch-filter for more infos.

       -j, --branch-filter
           Enable taken branch stack sampling. Each sample captures a series
           of consecutive taken branches. The number of branches captured
           with each sample depends on the underlying hardware, the type of
           branches of interest, and the executed code. It is possible to
           select the types of branches captured by enabling filters. The
           following filters are defined:

           •   any: any type of branches

           •   any_call: any function call or system call

           •   any_ret: any function return or system call return

           •   ind_call: any indirect branch

           •   call: direct calls, including far (to/from kernel) calls

           •   u: only when the branch target is at the user level

           •   k: only when the branch target is in the kernel

           •   hv: only when the target is at the hypervisor level

           •   in_tx: only when the target is in a hardware transaction

           •   no_tx: only when the target is not in a hardware transaction

           •   abort_tx: only when the target is a hardware transaction

           •   cond: conditional branches

           •   save_type: save branch type during sampling in case binary is
               not available later

           The option requires at least one branch type among any, any_call,
           any_ret, ind_call, cond. The privilege levels may be omitted, in
           which case, the privilege levels of the associated event are
           applied to the branch filter. Both kernel (k) and hypervisor (hv)
           privilege levels are subject to permissions. When sampling on
           multiple events, branch stack sampling is enabled for all the
           sampling events. The sampled branch type is the same for all
           events. The various filters must be specified as a comma
           separated list: --branch-filter any_ret,u,k Note that this
           feature may not be available on all processors.

           Enable weightened sampling. An additional weight is recorded per
           sample and can be displayed with the weight and local_weight sort
           keys. This currently works for TSX abort events and some memory
           events in precise mode on modern Intel CPUs.

           Record events of type PERF_RECORD_NAMESPACES. This enables
           cgroup_id sort key.

           Record events of type PERF_RECORD_CGROUP. This enables cgroup
           sort key.

           Record transaction flags for transaction related events.

           Use per-thread mmaps. By default per-cpu mmaps are created. This
           option overrides that and uses per-thread mmaps. A side-effect of
           that is that inheritance is automatically disabled. --per-thread
           is ignored with a warning if combined with -a or -C options.

       -D, --delay=
           After starting the program, wait msecs before measuring (-1:
           start with events disabled). This is useful to filter out the
           startup phase of the program, which is often very different.

       -I, --intr-regs
           Capture machine state (registers) at interrupt, i.e., on counter
           overflows for each sample. List of captured registers depends on
           the architecture. This option is off by default. It is possible
           to select the registers to sample using their symbolic names,
           e.g. on x86, ax, si. To list the available registers use
           --intr-regs=\?. To name registers, pass a comma separated list
           such as --intr-regs=ax,bx. The list of register is architecture

           Similar to -I, but capture user registers at sample time. To list
           the available user registers use --user-regs=\?.

           Record running and enabled time for read events (:S)

       -k, --clockid
           Sets the clock id to use for the various time fields in the
           perf_event_type records. See clock_gettime(). In particular
           CLOCK_MONOTONIC and CLOCK_MONOTONIC_RAW are supported, some
           events might also allow CLOCK_BOOTTIME, CLOCK_REALTIME and

       -S, --snapshot
           Select AUX area tracing Snapshot Mode. This option is valid only
           with an AUX area tracing event. Optionally, certain snapshot
           capturing parameters can be specified in a string that follows
           this option: e: take one last snapshot on exit; guarantees that
           there is at least one snapshot in the output file; <size>: if the
           PMU supports this, specify the desired snapshot size.

       In Snapshot Mode trace data is captured only when signal SIGUSR2 is
       received and on exit if the above e option is given.

           Select AUX area sampling. At least one of the events selected by
           the -e option must be an AUX area event. Samples on other events
           will be created containing data from the AUX area. Optionally
           sample size may be specified, otherwise it defaults to 4KiB.

           When processing pre-existing threads /proc/XXX/mmap, it may take
           a long time, because the file may be huge. A time out is needed
           in such cases. This option sets the time out limit. The default
           value is 500 ms.

           Record context switch events i.e. events of type
           (e.g. Intel PT or CoreSight) switch events will be enabled
           automatically, which can be suppressed by by the option

           Path to clang binary to use for compiling BPF scriptlets.
           (enabled when BPF support is on)

           Options passed to clang when compiling BPF scriptlets. (enabled
           when BPF support is on)

           Specify vmlinux path which has debuginfo. (enabled when BPF
           prologue is on)

           Record build-id of all DSOs regardless whether it’s actually hit
           or not.

           Use <n> control blocks in asynchronous (Posix AIO) trace writing
           mode (default: 1, max: 4). Asynchronous mode is supported only
           when linking Perf tool with libc library providing implementation
           for Posix AIO API.

           Set affinity mask of trace reading thread according to the policy
           defined by mode value: node - thread affinity mask is set to NUMA
           node cpu mask of the processed mmap buffer cpu - thread affinity
           mask is set to cpu of the processed mmap buffer

           Specify minimal number of bytes that is extracted from mmap data
           pages and processed for output. One can specify the number using
           B/K/M/G suffixes.

       The maximal allowed value is a quarter of the size of mmaped data

       The default option value is 1 byte which means that every time that
       the output writing thread finds some new data in the mmaped buffer
       the data is extracted, possibly compressed (-z) and written to the
       output, or pipe.

       Larger data chunks are compressed more effectively in comparison to
       smaller chunks so extraction of larger chunks from the mmap data
       pages is preferable from the perspective of output size reduction.

       Also at some cases executing less output write syscalls with bigger
       data size can take less time than executing more output write
       syscalls with smaller data size thus lowering runtime profiling

       -z, --compression-level[=n]
           Produce compressed trace using specified level n (default: 1 -
           fastest compression, 22 - smallest trace)

           Configure all used events to run in kernel space.

           Configure all used events to run in user space.

           Collect callchains only from kernel space. I.e. this option sets
           perf_event_attr.exclude_callchain_user to 1.

           Collect callchains only from user space. I.e. this option sets
           perf_event_attr.exclude_callchain_kernel to 1.

       Don’t use both --kernel-callchains and --user-callchains at the same
       time or no callchains will be collected.

       --timestamp-filename Append timestamp to output file name.

           Record timestamp boundary (time of first/last samples).

           Generate multiple files, timestamp prefixed, switching
           to a new one based on mode value: "signal" - when receiving a
           SIGUSR2 (default value) or <size> - when reaching the size
           threshold, size is expected to be a number with appended unit
           character - B/K/M/G <time> - when reaching the time threshold,
           size is expected to be a number with appended unit character -

               Note: the precision of  the size  threshold  hugely depends
               on your configuration  - the number and size of  your  ring
               buffers (-m). It is generally more precise for higher sizes
               (like >5M), for lower values expect different sizes.

       A possible use case is to, given an external event, slice the file that gets then processed, possibly via a perf script,
       to decide if that particular snapshot should be kept or

       Implies --timestamp-filename, --no-buildid and --no-buildid-cache.
       The reason for the latter two is to reduce the data file switching
       overhead. You can still switch them on with:

           --switch-output --no-no-buildid  --no-no-buildid-cache

           Events that will cause the switch of the file,
           auto-selecting --switch-output=signal, the results are similar as
           internally the side band thread will also send a SIGUSR2 to the
           main one.

       Uses the same syntax as --event, it will just not be recorded,
       serving only to switch the file as soon as the
       --switch-output event is processed by a separate sideband thread.

       This sideband thread is also used to other purposes, like processing
       the PERF_RECORD_BPF_EVENT records as they happen, asking the kernel
       for extra BPF information, etc.

           When rotating with --switch-output, only keep N files.

           Parse options then exit. --dry-run can be used to detect errors
           in cmdline options.

       perf record --dry-run -e can act as a BPF script compiler if
       llvm.dump-obj in config file is set to true.

           Instead of collecting non-sample events (for example, fork, comm,
           mmap) at the beginning of record, collect them during finalizing
           an output file. The collected non-sample events reflects the
           status of the system when record is finished.

           Makes all events use an overwritable ring buffer. An overwritable
           ring buffer works like a flight recorder: when it gets full, the
           kernel will overwrite the oldest records, that thus will never
           make it to the file.

       When --overwrite and --switch-output are used perf records and drops
       events until it receives a signal, meaning that something unusual was
       detected that warrants taking a snapshot of the most current events,
       those fitting in the ring buffer at that moment.

       overwrite attribute can also be set or canceled for an event using
       config terms. For example: cycles/overwrite/ and

       Implies --tail-synthesize.

           Make a copy of /proc/kcore and place it into a directory with the
           perf data file.

           Limit the sample data max size, <size> is expected to be a number
           with appended unit character - B/K/M/G

           The number of threads to run when synthesizing events for
           existing processes. By default, the number of threads equals 1.

       --control=fifo:ctl-fifo[,ack-fifo], --control=fd:ctl-fd[,ack-fd]
           ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as
           follows. Listen on ctl-fd descriptor for command to control
           measurement (enable: enable events, disable: disable events,
           snapshot: AUX area tracing snapshot). Measurements can be started
           with events disabled using --delay=-1 option. Optionally send
           control command completion (ack\n) to ack-fd descriptor to
           synchronize with the controlling process. Example of bash shell
           script to enable and disable events during measurements:



               test -p ${ctl_fifo} && unlink ${ctl_fifo}
               mkfifo ${ctl_fifo}
               exec {ctl_fd}<>${ctl_fifo}

               test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo}
               mkfifo ${ctl_ack_fifo}
               exec {ctl_fd_ack}<>${ctl_ack_fifo}

               perf record -D -1 -e cpu-cycles -a               \
                           --control fd:${ctl_fd},${ctl_fd_ack} \
                           -- sleep 30 &

               sleep 5  && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})"
               sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})"

               exec {ctl_fd_ack}>&-
               unlink ${ctl_ack_fifo}

               exec {ctl_fd}>&-
               unlink ${ctl_fifo}

               wait -n ${perf_pid}
               exit $?

SEE ALSO         top

       perf-stat(1), perf-list(1), perf-intel-pt(1)

COLOPHON         top

       This page is part of the perf (Performance analysis tools for Linux
       (in Linux source tree)) project.  Information about the project can
       be found at ⟨⟩.  If
       you have a bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on
       2020-11-01.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-11-01.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

perf                             2020-09-04                   PERF-RECORD(1)

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