# perf-record

## NAME



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


## SYNOPSIS



           _perf record_ [-e <EVENT> | --event=EVENT] [-a] <command>
           _perf record_ [-e <EVENT> | --event=EVENT] [-a] -- <command> [<options>]
    


## DESCRIPTION



           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



           <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



           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).
    


* * *