perf-record(1) — Linux manual page

NAME \| SYNOPSIS \| DESCRIPTION \| OPTIONS \| INTEL HYBRID SUPPORT \| SEE ALSO \| COLOPHON

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

NAME top

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

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 perf.data - without displaying anything.

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

OPTIONS top

<command>...
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 in the form of rN where N is a hexadecimal
value that represents the raw register encoding with the
layout of the event control registers as described by
entries in /sys/bus/event_source/devices/cpu/format/*.

• 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
pmu/config=M,config1=N,config3=K/

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:
/sys/bus/event_source/devices/<pmu>/format/*

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-action': "pause" or "resume" to pause or resume an AUX
area event (the group leader) when this event occurs.
"start-paused" on an AUX area event itself, will
start in a paused state.
- '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 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.

--filter=<filter>
Event filter. This option should follow an event selector
(-e). If the event is a tracepoint, the filter string will be
parsed by the kernel. If the event is a hardware trace PMU
(e.g. Intel PT or CoreSight), it’ll be processed as an address
filter. Otherwise it means a general filter using BPF which
can be applied for any kind of event.

• 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
/sys/bus/event_source/devices/<pmu>/nr_addr_filters.

Address filters have the format:

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

Where:
- '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
file.

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

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.

• bpf filters

A BPF filter can access the sample data and make a decision based on the
data. Users need to set an appropriate sample type to use the BPF
filter. BPF filters need root privilege.

The sample data field can be specified in lower case letter. Multiple
filters can be separated with comma. For example,

--filter 'period > 1000, cpu == 1'
or
--filter 'mem_op == load || mem_op == store, mem_lvl > l1'

The former filter only accept samples with period greater than 1000 AND
CPU number is 1. The latter one accepts either load and store memory
operations but it should have memory level above the L1. Since the
mem_op and mem_lvl fields come from the (memory) data_source, it'd only
work with some events which set the data_source field.

Also user should request to collect that information (with -d option in
the above case). Otherwise, the following message will be shown.

$ sudo perf record -e cycles --filter 'mem_op == load'
Error: cycles event does not have PERF_SAMPLE_DATA_SRC
Hint: please add -d option to perf record.
failed to set filter "BPF" on event cycles with 22 (Invalid argument)

Essentially the BPF filter expression is:

<term> <operator> <value> (("," | "||") <term> <operator> <value>)*

The <term> can be one of:
ip, id, tid, pid, cpu, time, addr, period, txn, weight, phys_addr,
code_pgsz, data_pgsz, weight1, weight2, weight3, ins_lat, retire_lat,
p_stage_cyc, mem_op, mem_lvl, mem_snoop, mem_remote, mem_lock,
mem_dtlb, mem_blk, mem_hops, uid, gid

The <operator> can be one of:
==, !=, >, >=, <, <=, &

The <value> can be one of:
<number> (for any term)
na, load, store, pfetch, exec (for mem_op)
l1, l2, l3, l4, cxl, io, any_cache, lfb, ram, pmem (for mem_lvl)
na, none, hit, miss, hitm, fwd, peer (for mem_snoop)
remote (for mem_remote)
na, locked (for mem_locked)
na, l1_hit, l1_miss, l2_hit, l2_miss, any_hit, any_miss, walk, fault (for mem_dtlb)
na, by_data, by_addr (for mem_blk)
hops0, hops1, hops2, hops3 (for mem_hops)

--exclude-perf
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 &&.

--latency
Enable data collection for latency profiling. Use perf report
--latency for latency-centric profile.

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

-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 --inherit.

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

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

--no-buffering
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.

--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 in bytes with appended unit character - B/K/M/G.
The size is rounded up to the nearest power-of-two page value.
By adding a comma, an additional parameter with the same
semantics used for the normal mmap areas can be specified for
AUX tracing area.

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

--call-graph
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
CONFIG_UNWINDER_FRAME_POINTER (fp) or CONFIG_UNWINDER_ORC (orc)

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
facility).

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".

When "fp" recording is used, perf tries to save stack entries
up to the number specified in sysctl.kernel.perf_event_max_stack
by default. User can change the number by passing it after comma
like "--call-graph fp,32".

-q, --quiet
Don’t print any warnings or messages, 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. Implies
--sample-mem-info.

--phys-data
Record the sample physical addresses.

--data-page-size
Record the sampled data address data page size.

--code-page-size
Record the sampled code address (ip) page size

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

-P, --period
Record the sample period.

--sample-cpu
Record the sample cpu.

--sample-identifier
Record the sample identifier i.e. PERF_SAMPLE_IDENTIFIER bit
set in the sample_type member of the struct perf_event_attr
argument to the perf_event_open system call.

--sample-mem-info
Record the sample data source information for memory
operations. It requires hardware supports and may work on
specific events only. Please consider using perf mem record
instead if you’re not sure.

-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 CPUs.

User space tasks can migrate between CPUs, so when tracing
selected CPUs, a dummy event is created to track sideband for all
CPUs.

-B, --no-buildid
Do not save the build ids of binaries in the perf.data 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 "record.build-id" 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 perf.data file (which
includes buildids) is sufficient. You can also set the
"record.build-id" config variable to no-cache to have the same
effect.

-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

• ind_jmp: any indirect jump

• 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
abort

• cond: conditional branches

• call_stack: save call stack

• no_flags: don’t save branch flags e.g prediction,
misprediction etc

• no_cycles: don’t save branch cycles

• hw_index: save branch hardware index

• save_type: save branch type during sampling in case binary
is not available later For the platforms with Intel Arch
LBR support (12th-Gen+ client or 4th-Gen Xeon+ server),
the save branch type is unconditionally enabled when the
taken branch stack sampling is enabled.

• priv: save privilege state during sampling in case binary
is not available later

• counter: save occurrences of the event since the last
branch entry. Currently, the feature is only supported by
a newer CPU, e.g., Intel Sierra Forest and later
platforms. An error out is expected if it’s used on the
unsupported kernel or CPUs.

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.

-W, --weight
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.

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

--all-cgroups
Record events of type PERF_RECORD_CGROUP. This enables cgroup
sort key.

--transaction
Record transaction flags for transaction related events.

--per-thread
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), or enable events only for
specified ranges of msecs (e.g. -D 10-20,30-40 means wait 10
msecs, enable for 10 msecs, wait 10 msecs, enable for 10
msecs, then stop). Note, delaying enabling of events 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 dependent.

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

--running-time
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
CLOCK_TAI.

-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.

--aux-sample[=OPTIONS]
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.

--proc-map-timeout
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.

--switch-events
Record context switch events i.e. events of type
PERF_RECORD_SWITCH or PERF_RECORD_SWITCH_CPU_WIDE. In some
cases (e.g. Intel PT, CoreSight or Arm SPE) switch events will
be enabled automatically, which can be suppressed by by the
option --no-switch-events.

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

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

--buildid-mmap
Legacy record build-id in map events option which is now the
default. Behaves indentically to --no-buildid. Disable with
--no-buildid-mmap.

--aio[=n]
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.

--affinity=mode
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

--mmap-flush=number
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
pages.

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, perf.data 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 overhead.

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

--all-kernel
Configure all used events to run in kernel space.

--all-user
Configure all used events to run in user space.

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

--user-callchains
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.

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

--switch-output[=mode]
Generate multiple perf.data 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 -
s/m/h/d

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
perf.data file that gets then processed, possibly via a perf
script, to decide if that particular perf.data snapshot should be
kept or not.

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

--switch-output-event
Events that will cause the switch of the perf.data 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 perf.data 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.

--switch-max-files=N
When rotating perf.data with --switch-output, only keep N
files.

--dry-run
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.

--synth=TYPE
Collect and synthesize given type of events (comma separated).
Note that this option controls the synthesis from the /proc
filesystem which represent task status for pre-existing
threads.

Kernel (and some other) events are recorded regardless of the
choice in this option. For example, --synth=no would have MMAP
events for kernel and modules.

Available types are:

• task - synthesize FORK and COMM events for each task

• mmap - synthesize MMAP events for each process (implies task)

• cgroup - synthesize CGROUP events for each cgroup

• all - synthesize all events (default)

• no - do not synthesize any of the above events

--tail-synthesize
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.

--overwrite
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 perf.data
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
instructions/no-overwrite/.

Implies --tail-synthesize.

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

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

--num-thread-synthesize
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.

Available commands:

• enable : enable events

• disable : disable events

• enable name : enable event name

• disable name : disable event name

• snapshot : AUX area tracing snapshot).

• stop : stop perf record

• ping : ping

• 'evlist [-v|-g|-F] : display all events

-F Show just the sample frequency used for each event.
-v Show all fields.
-g Show event group information.

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:

#!/bin/bash

ctl_dir=/tmp/

ctl_fifo=${ctl_dir}perf_ctl.fifo
test -p ${ctl_fifo} && unlink ${ctl_fifo}
mkfifo ${ctl_fifo}
exec {ctl_fd}<>${ctl_fifo}

ctl_ack_fifo=${ctl_dir}perf_ctl_ack.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 &
perf_pid=$!

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 $?

--threads=<spec>
Write collected trace data into several data files using
parallel threads. <spec> value can be user defined list of
masks. Masks separated by colon define CPUs to be monitored by
a thread and affinity mask of that thread is separated by
slash:

<cpus mask 1>/<affinity mask 1>:<cpus mask 2>/<affinity mask 2>:...

CPUs or affinity masks must not overlap with other corresponding
masks. Invalid CPUs are ignored, but masks containing only invalid
CPUs are not allowed.

For example user specification like the following:

0,2-4/2-4:1,5-7/5-7

specifies parallel threads layout that consists of two threads,
the first thread monitors CPUs 0 and 2-4 with the affinity mask
2-4, the second monitors CPUs 1 and 5-7 with the affinity mask
5-7.

<spec> value can also be a string meaning predefined parallel
threads layout:

• cpu - create new data streaming thread for every monitored cpu

• core - create new thread to monitor CPUs grouped by a core

• package - create new thread to monitor CPUs grouped by a
package

• numa - create new threed to monitor CPUs grouped by a NUMA
domain

Predefined layouts can be used on systems with large number of
CPUs in order not to spawn multiple per-cpu streaming threads but
still avoid LOST events in data directory files. Option specified
with no or empty value defaults to CPU layout. Masks defined or
provided by the option value are filtered through the mask
provided by -C option.

--debuginfod[=URLs]
Specify debuginfod URL to be used when cacheing perf.data
binaries, it follows the same syntax as the DEBUGINFOD_URLS
variable, like:

http://192.168.122.174:8002

If the URLs is not specified, the value of DEBUGINFOD_URLS
system environment variable is used.

--off-cpu
Enable off-cpu profiling with BPF. The BPF program will
collect task scheduling information with (user) stacktrace and
save them as sample data of a software event named
"offcpu-time". The sample period will have the time the task
slept in nanoseconds.

Note that BPF can collect stack traces using frame pointer ("fp")
only, as of now. So the applications built without the frame
pointer might see bogus addresses.

off-cpu profiling consists two types of samples: direct samples, which
share the same behavior as regular samples, and the accumulated
samples, stored in BPF stack trace map, presented after all the regular
samples.

--off-cpu-thresh
Once a task’s off-cpu time reaches this threshold (in
milliseconds), it generates a direct off-cpu sample. The
default is 500ms.

--setup-filter=<action>
Prepare BPF filter to be used by regular users. The action
should be either "pin" or "unpin". The filter can be used
after it’s pinned.

INTEL HYBRID SUPPORT top

Support for Intel hybrid events within perf tools.

For some Intel platforms, such as AlderLake, which is hybrid
platform and it consists of atom cpu and core cpu. Each cpu has
dedicated event list. Part of events are available on core cpu,
part of events are available on atom cpu and even part of events
are available on both.

Kernel exports two new cpu pmus via sysfs:
/sys/bus/event_source/devices/cpu_core
/sys/bus/event_source/devices/cpu_atom

The cpus files are created under the directories. For example,

cat /sys/bus/event_source/devices/cpu_core/cpus 0-15

cat /sys/bus/event_source/devices/cpu_atom/cpus 16-23

It indicates cpu0-cpu15 are core cpus and cpu16-cpu23 are atom
cpus.

As before, use perf-list to list the symbolic event.

perf list

inst_retired.any [Fixed Counter: Counts the number of instructions
retired. Unit: cpu_atom] inst_retired.any [Number of instructions
retired. Fixed Counter - architectural event. Unit: cpu_core]

The Unit: xxx is added to brief description to indicate which pmu
the event is belong to. Same event name but with different pmu can
be supported.

Enable hybrid event with a specific pmu

To enable a core only event or atom only event, following syntax
is supported:

cpu_core/<event name>/
or
cpu_atom/<event name>/

For example, count the cycles event on core cpus.

perf stat -e cpu_core/cycles/

Create two events for one hardware event automatically

When creating one event and the event is available on both atom
and core, two events are created automatically. One is for atom,
the other is for core. Most of hardware events and cache events
are available on both cpu_core and cpu_atom.

For hardware events, they have pre-defined configs (e.g. 0 for
cycles). But on hybrid platform, kernel needs to know where the
event comes from (from atom or from core). The original perf event
type PERF_TYPE_HARDWARE can’t carry pmu information. So now this
type is extended to be PMU aware type. The PMU type ID is stored
at attr.config[63:32].

PMU type ID is retrieved from sysfs.
/sys/bus/event_source/devices/cpu_atom/type
/sys/bus/event_source/devices/cpu_core/type

The new attr.config layout for PERF_TYPE_HARDWARE:

PERF_TYPE_HARDWARE: 0xEEEEEEEE000000AA AA: hardware event ID
EEEEEEEE: PMU type ID

Cache event is similar. The type PERF_TYPE_HW_CACHE is extended to
be PMU aware type. The PMU type ID is stored at
attr.config[63:32].

The new attr.config layout for PERF_TYPE_HW_CACHE:

PERF_TYPE_HW_CACHE: 0xEEEEEEEE00DDCCBB BB: hardware cache ID CC:
hardware cache op ID DD: hardware cache op result ID EEEEEEEE: PMU
type ID

When enabling a hardware event without specified pmu, such as,
perf stat -e cycles -a (use system-wide in this example), two
events are created automatically.

------------------------------------------------------------
perf_event_attr:
size 120
config 0x400000000
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
exclude_guest 1
------------------------------------------------------------

and

------------------------------------------------------------
perf_event_attr:
size 120
config 0x800000000
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
exclude_guest 1
------------------------------------------------------------

type 0 is PERF_TYPE_HARDWARE. 0x4 in 0x400000000 indicates it’s
cpu_core pmu. 0x8 in 0x800000000 indicates it’s cpu_atom pmu (atom
pmu type id is random).

The kernel creates cycles (0x400000000) on cpu0-cpu15 (core cpus),
and create cycles (0x800000000) on cpu16-cpu23 (atom cpus).

For perf-stat result, it displays two events:

Performance counter stats for 'system wide':

6,744,979 cpu_core/cycles/
1,965,552 cpu_atom/cycles/

The first cycles is core event, the second cycles is atom event.

Thread mode example:

perf-stat reports the scaled counts for hybrid event and with a
percentage displayed. The percentage is the event’s running
time/enabling time.

One example, triad_loop runs on cpu16 (atom core), while we can
see the scaled value for core cycles is 160,444,092 and the
percentage is 0.47%.

perf stat -e cycles -- taskset -c 16 ./triad_loop

As previous, two events are created.

.ft C
perf_event_attr:
size 120
config 0x400000000
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
enable_on_exec 1
exclude_guest 1
.ft

and

.ft C
perf_event_attr:
size 120
config 0x800000000
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
enable_on_exec 1
exclude_guest 1
.ft

Performance counter stats for 'taskset -c 16 ./triad_loop':

233,066,666 cpu_core/cycles/ (0.43%)
604,097,080 cpu_atom/cycles/ (99.57%)

perf-record:

If there is no -e specified in perf record, on hybrid platform, it
creates two default cycles and adds them to event list. One is for
core, the other is for atom.

perf-stat:

If there is no -e specified in perf stat, on hybrid platform,
besides of software events, following events are created and added
to event list in order.

cpu_core/cycles/, cpu_atom/cycles/, cpu_core/instructions/,
cpu_atom/instructions/, cpu_core/branches/, cpu_atom/branches/,
cpu_core/branch-misses/, cpu_atom/branch-misses/

Of course, both perf-stat and perf-record support to enable hybrid
event with a specific pmu.

e.g. perf stat -e cpu_core/cycles/ perf stat -e cpu_atom/cycles/
perf stat -e cpu_core/r1a/ perf stat -e cpu_atom/L1-icache-loads/
perf stat -e cpu_core/cycles/,cpu_atom/instructions/ perf stat -e
{cpu_core/cycles/,cpu_core/instructions/}

But {cpu_core/cycles/,cpu_atom/instructions/} will return warning
and disable grouping, because the pmus in group are not matched
(cpu_core vs. cpu_atom).

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 
       ⟨https://perf.wiki.kernel.org/index.php/Main_Page⟩.  If you have a
       bug report for this manual page, send it to
       linux-kernel@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git⟩
       on 2025-08-11.  (At that time, the date of the most recent commit
       that was found in the repository was 2025-08-10.)  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 man-pages@man7.org

perf                            2025-07-25                 PERF-RECORD(1)

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