trace-cmd-record(1) — Linux manual page


TRACE-CMD-RECORD(1)                                  TRACE-CMD-RECORD(1)

NAME         top

       trace-cmd-record - record a trace from the Ftrace Linux internal

SYNOPSIS         top

       trace-cmd record [OPTIONS] [command]

DESCRIPTION         top

       The trace-cmd(1) record command will set up the Ftrace Linux
       kernel tracer to record the specified plugins or events that
       happen while the command executes. If no command is given, then
       it will record until the user hits Ctrl-C.

       The record command of trace-cmd will set up the Ftrace tracer to
       start tracing the various events or plugins that are given on the
       command line. It will then create a number of tracing processes
       (one per CPU) that will start recording from the kernel ring
       buffer straight into temporary files. When the command is
       complete (or Ctrl-C is hit) all the files will be combined into a
       trace.dat file that can later be read (see trace-cmd-report(1)).

OPTIONS         top

       -p tracer
           Specify a tracer. Tracers usually do more than just trace an
           event. Common tracers are: function, function_graph,
           preemptirqsoff, irqsoff, preemptoff and wakeup. A tracer must
           be supported by the running kernel. To see a list of
           available tracers, see trace-cmd-list(1).

       -e event
           Specify an event to trace. Various static trace points have
           been added to the Linux kernel. They are grouped by subsystem
           where you can enable all events of a given subsystem or
           specify specific events to be enabled. The event is of the
           format "subsystem:event-name". You can also just specify the
           subsystem without the :event-name or the event-name without
           the "subsystem:". Using "-e sched_switch" will enable the
           "sched_switch" event where as, "-e sched" will enable all
           events under the "sched" subsystem.

               The 'event' can also contain glob expressions. That is, "*stat*" will
               select all events (or subsystems) that have the characters "stat" in their

               The keyword 'all' can be used to enable all events.

           Every event that is being recorded has its output format file
           saved in the output file to be able to display it later. But
           if other events are enabled in the trace without trace-cmd’s
           knowledge, the formats of those events will not be recorded
           and trace-cmd report will not be able to display them. If
           this is the case, then specify the -a option and the format
           for all events in the system will be saved.

           Enable a stacktrace on each event. For example:

                         <idle>-0     [003] 58549.289091: sched_switch:         kworker/0:1:0 [120] R ==> trace-cmd:2603 [120]
                         <idle>-0     [003] 58549.289092: kernel_stack:         <stack trace>
               => schedule (ffffffff814b260e)
               => cpu_idle (ffffffff8100a38c)
               => start_secondary (ffffffff814ab828)

           Enable a stack trace on all functions. Note this is only
           applicable for the "function" plugin tracer, and will only
           take effect if the -l option is used and succeeds in limiting
           functions. If the function tracer is not filtered, and the
           stack trace is enabled, you can live lock the machine.

       -f filter
           Specify a filter for the previous event. This must come after
           a -e. This will filter what events get recorded based on the
           content of the event. Filtering is passed to the kernel
           directly so what filtering is allowed may depend on what
           version of the kernel you have. Basically, it will let you
           use C notation to check if an event should be processed or

               ==, >=, <=, >, <, &, |, && and ||

           The above are usually safe to use to compare fields.

           Do not filter out the trace-cmd threads. By default, the
           threads are filtered out to not be traced by events. This
           option will have the trace-cmd threads also be traced.

       -R trigger
           Specify a trigger for the previous event. This must come
           after a -e. This will add a given trigger to the given event.
           To only enable the trigger and not the event itself, then
           place the event after the -v option.

               See Documentation/trace/events.txt in the Linux kernel source for more
               information on triggers.

           This will cause all events specified after it on the command
           line to not be traced. This is useful for selecting a
           subsystem to be traced but to leave out various events. For
           Example: "-e sched -v -e "*stat\*"" will enable all events in
           the sched subsystem except those that have "stat" in their

               Note: the *-v* option was taken from the way grep(1) inverts the following

           This will filter only the executable that is given on the
           command line. If no command is given, then it will filter
           itself (pretty pointless). Using -F will let you trace only
           events that are caused by the given command.

       -P pid
           Similar to -F but lets you specify a process ID to trace.

           Used with either -F (or -P if kernel supports it) to trace
           the process' children too.

           Execute the specified command as given user.

       -C clock
           Set the trace clock to "clock".

               Use trace-cmd(1) list -C to see what clocks are available.

       -o output-file
           By default, trace-cmd report will create a trace.dat file.
           You can specify a different file to write to with the -o

       -l function-name
           This will limit the function and function_graph tracers to
           only trace the given function name. More than one -l may be
           specified on the command line to trace more than one
           function. The limited use of glob expressions are also
           allowed. These are match* to only filter functions that start
           with match.  *match to only filter functions that end with
           match.  *match\* to only filter on functions that contain

       -g function-name
           This option is for the function_graph plugin. It will graph
           the given function. That is, it will only trace the function
           and all functions that it calls. You can have more than one
           -g on the command line.

       -n function-name
           This has the opposite effect of -l. The function given with
           the -n option will not be traced. This takes precedence, that
           is, if you include the same function for both -n and -l, it
           will not be traced.

           Some tracer plugins enable the function tracer by default.
           Like the latency tracers. This option prevents the function
           tracer from being enabled at start up.

           The option -d will try to use the function-trace option to
           disable the function tracer (if available), otherwise it
           defaults to the proc file: /proc/sys/kernel/ftrace_enabled,
           but will not touch it if the function-trace option is
           available. The -D option will disable both the ftrace_enabled
           proc file as well as the function-trace option if it exists.

               Note, this disable function tracing for all users, which includes users
               outside of ftrace tracers (stack_tracer, perf, etc).

       -O option
           Ftrace has various options that can be enabled or disabled.
           This allows you to set them. Appending the text no to an
           option disables it. For example: "-O nograph-time" will
           disable the "graph-time" Ftrace option.

       -s interval
           The processes that trace-cmd creates to record from the ring
           buffer need to wake up to do the recording. Setting the
           interval to zero will cause the processes to wakeup every
           time new data is written into the buffer. But since Ftrace is
           recording kernel activity, the act of this processes going
           back to sleep may cause new events into the ring buffer which
           will wake the process back up. This will needlessly add extra
           data into the ring buffer.

               The 'interval' metric is microseconds. The default is set to 1000 (1 ms).
               This is the time each recording process will sleep before waking up to
               record any new data that was written to the ring buffer.

       -r priority
           The priority to run the capture threads at. In a busy system
           the trace capturing threads may be staved and events can be
           lost. This increases the priority of those threads to the
           real time (FIFO) priority. But use this option with care, it
           can also change the behaviour of the system being traced.

       -b size
           This sets the ring buffer size to size kilobytes. Because the
           Ftrace ring buffer is per CPU, this size is the size of each
           per CPU ring buffer inside the kernel. Using "-b 10000" on a
           machine with 4 CPUs will make Ftrace have a total buffer size
           of 40 Megs.

       -B buffer-name
           If the kernel supports multiple buffers, this will add a
           buffer with the given name. If the buffer name already
           exists, that buffer is just reset and will not be deleted at
           the end of record execution. If the buffer is created, it
           will be removed at the end of execution (unless the -k is
           set, or start command was used).

               After a buffer name is stated, all events added after that will be
               associated with that buffer. If no buffer is specified, or an event
               is specified before a buffer name, it will be associated with the
               main (toplevel) buffer.

               trace-cmd record -e sched -B block -e block -B time -e timer sleep 1

               The above is will enable all sched events in the main buffer. It will
               then create a 'block' buffer instance and enable all block events within
               that buffer. A 'time' buffer instance is created and all timer events
               will be enabled for that event.

       -m size
           The max size in kilobytes that a per cpu buffer should be.
           Note, due to rounding to page size, the number may not be
           totally correct. Also, this is performed by switching between
           two buffers that are half the given size thus the output may
           not be of the given size even if much more was written.

               Use this to prevent running out of diskspace for long runs.

       -M cpumask
           Set the cpumask for to trace. It only affects the last buffer
           instance given. If supplied before any buffer instance, then
           it affects the main buffer. The value supplied must be a hex

               trace-cmd record -p function -M c -B events13 -e all -M 5

               If the -M is left out, then the mask stays the same. To enable all
               CPUs, pass in a value of '-1'.

           By default, when trace-cmd is finished tracing, it will reset
           the buffers and disable all the tracing that it enabled. This
           option keeps trace-cmd from disabling the tracer and reseting
           the buffer. This option is useful for debugging trace-cmd.

               Note: usually trace-cmd will set the "tracing_on" file back to what it
               was before it was called. This option will leave that file set to zero.

           By default, if an event is listed that trace-cmd does not
           find, it will exit with an error. This option will just
           ignore events that are listed on the command line but are not
           found on the system.

       -N host:port
           If another machine is running "trace-cmd listen", this option
           is used to have the data sent to that machine with UDP
           packets. Instead of writing to an output file, the data is
           sent off to a remote box. This is ideal for embedded machines
           with little storage, or having a single machine that will
           keep all the data in a single repository.

               Note: This option is not supported with latency tracer plugins:
                 wakeup, wakeup_rt, irqsoff, preemptoff and preemptirqsoff

           This option is used with -N, when there’s a need to send the
           live data with TCP packets instead of UDP. Although TCP is
           not nearly as fast as sending the UDP packets, but it may be
           needed if the network is not that reliable, the amount of
           data is not that intensive, and a guarantee is needed that
           all traced information is transfered successfully.

       -q | --quiet
           For use with recording an application. Suppresses normal
           output (except for errors) to allow only the application’s
           output to be displayed.

           With the --date option, "trace-cmd" will write timestamps
           into the trace buffer after it has finished recording. It
           will then map the timestamp to gettimeofday which will allow
           wall time output from the timestamps reading the created
           trace.dat file.

       --max-graph-depth depth
           Set the maximum depth the function_graph tracer will trace
           into a function. A value of one will only show where
           userspace enters the kernel but not any functions called in
           the kernel. The default is zero, which means no limit.

       --cmdlines-size size
           Set the number of entries the kernel tracing file
           "saved_cmdlines" can contain. This file is a circular buffer
           which stores the mapping between cmdlines and PIDs. If full,
           it leads to unresolved cmdlines ("<...>") within the trace.
           The kernel default value is 128.

       --module module
           Filter a module’s name in function tracing. It is equivalent
           to adding :mod:module after all other functions being
           filtered. If no other function filter is listed, then all
           modules functions will be filtered in the filter.

               '--module snd'  is equivalent to  '-l :mod:snd'

               '--module snd -l "*jack*"' is equivalent to '-l "*jack*:mod:snd"'

               '--module snd -n "*"' is equivalent to '-n :mod:snd'

           Save the traced process address map into the trace.dat file.
           The traced processes can be specified using the option -P, or
           as a given command.

           With the --profile option, "trace-cmd" will enable tracing
           that can be used with trace-cmd-report(1) --profile option.
           If a tracer -p is not set, and function graph depth is
           supported by the kernel, then the function_graph tracer will
           be enabled with a depth of one (only show where userspace
           enters into the kernel). It will also enable various
           tracepoints with stack tracing such that the report can show
           where tasks have been blocked for the longest time.

               See trace-cmd-profile(1) for more details and examples.

           Set interrupt (soft and hard) events as global (associated to
           CPU instead of tasks). Only works for --profile.

       -H event-hooks
           Add custom event matching to connect any two events together.
           When not used with --profile, it will save the parameter and
           this will be used by trace-cmd report --profile, too. That

               trace-cmd record -H hrtimer_expire_entry,hrtimer/hrtimer_expire_exit,hrtimer,sp
               trace-cmd report --profile

               Will profile hrtimer_expire_entry and hrtimer_expire_ext times.

               See trace-cmd-profile(1) for format.

           (for --profile only) Only enable the tracer or events
           speficied on the command line. With this option, the
           function_graph tracer is not enabled, nor are any events
           (like sched_switch), unless they are specifically specified
           on the command line (i.e. -p function -e sched_switch -e

       --ts-offset offset
           Add an offset for the timestamp in the trace.dat file. This
           will add a offset option into the trace.dat file such that a
           trace-cmd report will offset all the timestamps of the events
           by the given offset. The offset is in raw units. That is, if
           the event timestamps are in nanoseconds the offset will also
           be in nanoseconds even if the displayed units are in

           Set the loop interval, in ms, for timestamps synchronization
           with guests: If a negative number is specified, timestamps
           synchronization is disabled If 0 is specified, no loop is
           performed - timestamps offset is calculated only twice," at
           the beginning and at the end of the trace. Timestamps
           synchronization with guests works only if there is support
           for VSOCK.\n"

           Have output go to stderr instead of stdout, but the output of
           the command executed will not be changed. This is useful if
           you want to monitor the output of the command being executed,
           but not see the output from trace-cmd.

EXAMPLES         top

       The basic way to trace all events:

            # trace-cmd record -e all ls > /dev/null
            # trace-cmd report
                  trace-cmd-13541 [003] 106260.693809: filemap_fault: address=0x128122 offset=0xce
                  trace-cmd-13543 [001] 106260.693809: kmalloc: call_site=81128dd4 ptr=0xffff88003dd83800 bytes_req=768 bytes_alloc=1024 gfp_flags=GFP_KERNEL|GFP_ZERO
                         ls-13545 [002] 106260.693809: kfree: call_site=810a7abb ptr=0x0
                         ls-13545 [002] 106260.693818: sys_exit_write:       0x1

       To use the function tracer with sched switch tracing:

            # trace-cmd record -p function -e sched_switch ls > /dev/null
            # trace-cmd report
                         ls-13587 [002] 106467.860310: function: hrtick_start_fair <-- pick_next_task_fair
                         ls-13587 [002] 106467.860313: sched_switch: prev_comm=trace-cmd prev_pid=13587 prev_prio=120 prev_state=R ==> next_comm=trace-cmd next_pid=13583 next_prio=120
                  trace-cmd-13585 [001] 106467.860314: function: native_set_pte_at <-- __do_fault
                  trace-cmd-13586 [003] 106467.860314: function:             up_read <-- do_page_fault
                         ls-13587 [002] 106467.860317: function:             __phys_addr <-- schedule
                  trace-cmd-13585 [001] 106467.860318: function: _raw_spin_unlock <-- __do_fault
                         ls-13587 [002] 106467.860320: function: native_load_sp0 <-- __switch_to
                  trace-cmd-13586 [003] 106467.860322: function: down_read_trylock <-- do_page_fault

       Here is a nice way to find what interrupts have the highest

            # trace-cmd record -p function_graph -e irq_handler_entry  -l do_IRQ sleep 10
            # trace-cmd report
                     <idle>-0     [000] 157412.933969: funcgraph_entry:                  |  do_IRQ() {
                     <idle>-0     [000] 157412.933974: irq_handler_entry:    irq=48 name=eth0
                     <idle>-0     [000] 157412.934004: funcgraph_exit:       + 36.358 us |  }
                     <idle>-0     [000] 157413.895004: funcgraph_entry:                  |  do_IRQ() {
                     <idle>-0     [000] 157413.895011: irq_handler_entry:    irq=48 name=eth0
                     <idle>-0     [000] 157413.895026: funcgraph_exit:                        + 24.014 us |  }
                     <idle>-0     [000] 157415.891762: funcgraph_entry:                  |  do_IRQ() {
                     <idle>-0     [000] 157415.891769: irq_handler_entry:    irq=48 name=eth0
                     <idle>-0     [000] 157415.891784: funcgraph_exit:       + 22.928 us |  }
                     <idle>-0     [000] 157415.934869: funcgraph_entry:                  |  do_IRQ() {
                     <idle>-0     [000] 157415.934874: irq_handler_entry:    irq=48 name=eth0
                     <idle>-0     [000] 157415.934906: funcgraph_exit:       + 37.512 us |  }
                     <idle>-0     [000] 157417.888373: funcgraph_entry:                  |  do_IRQ() {
                     <idle>-0     [000] 157417.888381: irq_handler_entry:    irq=48 name=eth0
                     <idle>-0     [000] 157417.888398: funcgraph_exit:       + 25.943 us |  }

       An example of the profile:

            # trace-cmd record --profile sleep 1
            # trace-cmd report --profile --comm sleep
           task: sleep-21611
             Event: sched_switch:R (1) Total: 99442 Avg: 99442 Max: 99442 Min:99442
                <stack> 1 total:99442 min:99442 max:99442 avg=99442
                  => ftrace_raw_event_sched_switch (0xffffffff8105f812)
                  => __schedule (0xffffffff8150810a)
                  => preempt_schedule (0xffffffff8150842e)
                  => ___preempt_schedule (0xffffffff81273354)
                  => cpu_stop_queue_work (0xffffffff810b03c5)
                  => stop_one_cpu (0xffffffff810b063b)
                  => sched_exec (0xffffffff8106136d)
                  => do_execve_common.isra.27 (0xffffffff81148c89)
                  => do_execve (0xffffffff811490b0)
                  => SyS_execve (0xffffffff811492c4)
                  => return_to_handler (0xffffffff8150e3c8)
                  => stub_execve (0xffffffff8150c699)
             Event: sched_switch:S (1) Total: 1000506680 Avg: 1000506680 Max: 1000506680 Min:1000506680
                <stack> 1 total:1000506680 min:1000506680 max:1000506680 avg=1000506680
                  => ftrace_raw_event_sched_switch (0xffffffff8105f812)
                  => __schedule (0xffffffff8150810a)
                  => schedule (0xffffffff815084b8)
                  => do_nanosleep (0xffffffff8150b22c)
                  => hrtimer_nanosleep (0xffffffff8108d647)
                  => SyS_nanosleep (0xffffffff8108d72c)
                  => return_to_handler (0xffffffff8150e3c8)
                  => tracesys_phase2 (0xffffffff8150c304)
             Event: sched_wakeup:21611 (1) Total: 30326 Avg: 30326 Max: 30326 Min:30326
                <stack> 1 total:30326 min:30326 max:30326 avg=30326
                  => ftrace_raw_event_sched_wakeup_template (0xffffffff8105f653)
                  => ttwu_do_wakeup (0xffffffff810606eb)
                  => ttwu_do_activate.constprop.124 (0xffffffff810607c8)
                  => try_to_wake_up (0xffffffff8106340a)

SEE ALSO         top

       trace-cmd(1), trace-cmd-report(1), trace-cmd-start(1),
       trace-cmd-stop(1), trace-cmd-extract(1), trace-cmd-reset(1),
       trace-cmd-split(1), trace-cmd-list(1), trace-cmd-listen(1),

AUTHOR         top

       Written by Steven Rostedt, <[1]>

RESOURCES         top


COPYING         top

       Copyright (C) 2010 Red Hat, Inc. Free use of this software is
       granted under the terms of the GNU Public License (GPL).

NOTES         top


COLOPHON         top

       This page is part of the trace-cmd (a front-end for Ftrace)
       project.  Information about the project can be found at [unknown
       -- if you know, please contact] If you have a
       bug report for this manual page, send it to Steven Rostedt
       <>.  This page was obtained from the project's
       upstream Git repository
       on 2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-20.)  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

                               06/09/2020            TRACE-CMD-RECORD(1)

Pages that refer to this page: trace-cmd(1)trace-cmd-check-events(1)trace-cmd-clear(1)trace-cmd-extract(1)trace-cmd-hist(1)trace-cmd-list(1)trace-cmd-listen(1)trace-cmd-mem(1)trace-cmd-options(1)trace-cmd-profile(1)trace-cmd-report(1)trace-cmd-reset(1)trace-cmd-restore(1)trace-cmd-show(1)trace-cmd-snapshot(1)trace-cmd-split(1)trace-cmd-stack(1)trace-cmd-start(1)trace-cmd-stat(1)trace-cmd-stop(1)trace-cmd-stream(1)trace-cmd.dat(5)