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 not.

               ==, >=, <=, >, <, &, |, && 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 names.

               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 option.

       -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 match.

       -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

           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

               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 number.

               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

       -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

           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 is:

               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 sched_wakeup)

       --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 microseconds.

           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 latency:

            # 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 2020-09-18.  (At that time, the date of the most recent commit
       that was found in the repository was 2020-07-22.)  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

                                 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)