PERF-TRACE(1)                    perf Manual                   PERF-TRACE(1)

NAME         top

       perf-trace - strace inspired tool

SYNOPSIS         top

       perf trace
       perf trace record

DESCRIPTION         top

       This command will show the events associated with the target,
       initially syscalls, but other system events like pagefaults, task
       lifetime events, scheduling events, etc.

       This is a live mode tool in addition to working with files
       like the other perf tools. Files can be generated using the perf
       record command but the session needs to include the raw_syscalls
       events (-e raw_syscalls:*). Alternatively, perf trace record can be
       used as a shortcut to automatically include the raw_syscalls events
       when writing events to a file.

       The following options apply to perf trace; options to perf trace
       record are found in the perf record man page.

OPTIONS         top

       -a, --all-cpus
           System-wide collection from all CPUs.

       -e, --expr, --event
           List of syscalls and other perf events (tracepoints, HW cache
           events, etc) to show. Globbing is supported, e.g.: "epoll_*",
           "msg", etc. See perf list for a complete list of events.
           Prefixing with ! shows all syscalls but the ones specified. You
           may need to escape it.

       -D msecs, --delay msecs
           After starting the program, wait msecs before measuring. This is
           useful to filter out the startup phase of the program, which is
           often very different.

       -o, --output=
           Output file name.

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

       -t, --tid=
           Record events on existing thread ID (comma separated list).

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

       -G, --cgroup
           Record events in threads in a cgroup.

               Look for cgroups to set at the /sys/fs/cgroup/perf_event directory, then
               remove the /sys/fs/cgroup/perf_event/ part and try:

               perf trace -G A -e sched:*switch

               Will set all raw_syscalls:sys_{enter,exit}, pgfault, vfs_getname, etc
               _and_ sched:sched_switch to the 'A' cgroup, while:

               perf trace -e sched:*switch -G A

               will only set the sched:sched_switch event to the 'A' cgroup, all the
               other events (raw_syscalls:sys_{enter,exit}, etc are left "without"
               a cgroup (on the root cgroup, sys wide, etc).

               Multiple cgroups:

               perf trace -G A -e sched:*switch -G B

               the syscall ones go to the 'A' cgroup, the sched:sched_switch goes
               to the 'B' cgroup.

           Filter out events for these pids and for trace itself (comma
           separated list).

       -v, --verbose=
           Verbosity level.

           Child tasks do not inherit counters.

       -m, --mmap-pages=
           Number of mmap data pages (must be a power of two) or size
           specification with appended unit character - B/K/M/G. The size is
           rounded up to have nearest pages power of two value.

       -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), Events are captured only when the
           thread executes on the designated CPUs. Default is to monitor all

           Show only events that had a duration greater than N.M ms.

           Accrue thread runtime and provide a summary at the end of the

           Show only syscalls that failed, i.e. that returned < 0.

       -i, --input
           Process events from a given perf data file.

       -T, --time
           Print full timestamp rather time relative to first sample.

           Show process COMM right beside its ID, on by default, disable
           with --no-comm.

       -s, --summary
           Show only a summary of syscalls by thread with min, max, and
           average times (in msec) and relative stddev.

       -S, --with-summary
           Show all syscalls followed by a summary by thread with min, max,
           and average times (in msec) and relative stddev.

           Show tool stats such as number of times fd→pathname was
           discovered thru hooking the open syscall return + vfs_getname or
           via reading /proc/pid/fd, etc.

       -f, --force
           Don’t complain, do it.

       -F=[all|min|maj], --pf=[all|min|maj]
           Trace pagefaults. Optionally, you can specify whether you want
           minor, major or all pagefaults. Default value is maj.

           Trace system calls. This options is enabled by default, disable
           with --no-syscalls.

       --call-graph [mode,type,min[,limit],order[,key][,branch]]
           Setup and enable call-graph (stack chain/backtrace) recording.
           See --call-graph section in perf-record and perf-report man pages
           for details. The ones that are most useful in perf trace are
           dwarf and lbr, where available, try: perf trace --call-graph

               Using this will, for the root user, bump the value of --mmap-pages to 4
               times the maximum for non-root users, based on the kernel.perf_event_mlock_kb
               sysctl. This is done only if the user doesn't specify a --mmap-pages value.

           Show the kernel callchains on the syscall exit path.

           Stop after processing N events. Note that strace-like events are
           considered only at exit time or when a syscall is interrupted,
           i.e. in those cases this option is equivalent to the number of
           lines printed.

           Set the stack depth limit when parsing the callchain, anything
           beyond the specified depth will be ignored. Note that at this
           point this is just about the presentation part, i.e. the kernel
           is still not limiting, the overhead of callchains needs to be set
           via the knobs in --call-graph dwarf.

               Implies '--call-graph dwarf' when --call-graph not present on the
               command line, on systems where DWARF unwinding was built in.

               Default: /proc/sys/kernel/perf_event_max_stack when present for
                        live sessions (without --input/-i), 127 otherwise.

           Set the stack depth limit when parsing the callchain, anything
           below the specified depth will be ignored. Disabled by default.

               Implies '--call-graph dwarf' when --call-graph not present on the
               command line, on systems where DWARF unwinding was built in.

           Print the PERF_RECORD_SAMPLE PERF_SAMPLE_ info for the
           raw_syscalls:sys_{enter,exit} tracepoints, for debugging.

           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.

           Do sorting on batches of events, use when noticing out of order
           events that may happen, for instance, when a thread gets migrated
           to a different CPU while processing a syscall.

PAGEFAULTS         top

       When tracing pagefaults, the format of the trace is as follows:

       <min|maj>fault [<ip.symbol>+<ip.offset>] ⇒ <addr.dso@addr.offset[1]>
       (<map type><addr level>).

       ·   min/maj indicates whether fault event is minor or major;

       ·   ip.symbol shows symbol for instruction pointer (the code that
           generated the fault); if no debug symbols available, perf trace
           will print raw IP;

       ·   addr.dso shows DSO for the faulted address;

       ·   map type is either d for non-executable maps or x for executable

       ·   addr level is either k for kernel dso or .  for user dso.

       For symbols resolution you may need to install debugging symbols.

       Please be aware that duration is currently always 0 and doesn’t
       reflect actual time it took for fault to be handled!

       When --verbose specified, perf trace tries to print all available
       information for both IP and fault address in the form of

EXAMPLES         top

       Trace only major pagefaults:

           $ perf trace --no-syscalls -F

       Trace syscalls, major and minor pagefaults:

           $ perf trace -F all

           1416.547 ( 0.000 ms): python/20235 majfault [CRYPTO_push_info_+0x0] => /lib/x86_64-linux-gnu/ (x.)

           As you can see, there was major pagefault in python process, from
           CRYPTO_push_info_ routine which faulted somewhere in

       Trace the first 4 open, openat or open_by_handle_at syscalls (in the
       future more syscalls may match here):

           $ perf trace -e open* --max-events 4
           [root@jouet perf]# trace -e open* --max-events 4
           2272.992 ( 0.037 ms): gnome-shell/1370 openat(dfd: CWD, filename: /proc/self/stat) = 31
           2277.481 ( 0.139 ms): gnome-shell/3039 openat(dfd: CWD, filename: /proc/self/stat) = 65
           3026.398 ( 0.076 ms): gnome-shell/3039 openat(dfd: CWD, filename: /proc/self/stat) = 65
           4294.665 ( 0.015 ms): sed/15879 openat(dfd: CWD, filename: /etc/, flags: CLOEXEC) = 3

       Trace the first minor page fault when running a workload:

           # perf trace -F min --max-stack=7 --max-events 1 sleep 1
              0.000 ( 0.000 ms): sleep/18006 minfault [__clear_user+0x1a] => 0x5626efa56080 (?k)
                                                __clear_user ([kernel.kallsyms])
                                                load_elf_binary ([kernel.kallsyms])
                                                search_binary_handler ([kernel.kallsyms])
                                                __do_execve_file.isra.33 ([kernel.kallsyms])
                                                __x64_sys_execve ([kernel.kallsyms])
                                                do_syscall_64 ([kernel.kallsyms])
                                                entry_SYSCALL_64 ([kernel.kallsyms])

       Trace the next min page page fault to take place on the first CPU:

           # perf trace -F min --call-graph=dwarf --max-events 1 --cpu 0
              0.000 ( 0.000 ms): Web Content/17136 minfault [js::gc::Chunk::fetchNextDecommittedArena+0x4b] => 0x7fbe6181b000 (?.)
                                                js::gc::FreeSpan::initAsEmpty (inlined)
                                                js::gc::Arena::setAsNotAllocated (inlined)
                                                js::gc::Chunk::fetchNextDecommittedArena (/usr/lib64/firefox/
                                                js::gc::Chunk::allocateArena (/usr/lib64/firefox/
                                                js::gc::GCRuntime::allocateArena (/usr/lib64/firefox/
                                                js::gc::ArenaLists::allocateFromArena (/usr/lib64/firefox/
                                                js::gc::GCRuntime::tryNewTenuredThing<JSString, (js::AllowGC)1> (inlined)
                                                js::AllocateString<JSString, (js::AllowGC)1> (/usr/lib64/firefox/
                                                js::Allocate<JSThinInlineString, (js::AllowGC)1> (inlined)
                                                JSThinInlineString::new_<(js::AllowGC)1> (inlined)
                                                AllocateInlineString<(js::AllowGC)1, unsigned char> (inlined)
                                                js::ConcatStrings<(js::AllowGC)1> (/usr/lib64/firefox/
                                                [0x18b26e6bc2bd] (/tmp/

       Trace the next two sched:sched_switch events, four block:*_plug
       events, the next block:*_unplug and the next three net:*dev_queue
       events, this last one with a backtrace of at most 16 entries, system

           # perf trace -e sched:*switch/nr=2/,block:*_plug/nr=4/,block:*_unplug/nr=1/,net:*dev_queue/nr=3,max-stack=16/
              0.000 :0/0 sched:sched_switch:swapper/2:0 [120] S ==> rcu_sched:10 [120]
              0.015 rcu_sched/10 sched:sched_switch:rcu_sched:10 [120] R ==> swapper/2:0 [120]
            254.198 irq/50-iwlwifi/680 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff93498051f600 len=66
                                                __dev_queue_xmit ([kernel.kallsyms])
            273.977 :0/0 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff93498051f600 len=78
                                                __dev_queue_xmit ([kernel.kallsyms])
            274.007 :0/0 net:net_dev_queue:dev=wlp3s0 skbaddr=0xffff93498051ff00 len=78
                                                __dev_queue_xmit ([kernel.kallsyms])
           2930.140 kworker/u16:58/2722 block:block_plug:[kworker/u16:58]
           2930.162 kworker/u16:58/2722 block:block_unplug:[kworker/u16:58] 1
           4466.094 jbd2/dm-2-8/748 block:block_plug:[jbd2/dm-2-8]
           8050.123 kworker/u16:30/2694 block:block_plug:[kworker/u16:30]
           8050.271 kworker/u16:30/2694 block:block_plug:[kworker/u16:30]

SEE ALSO         top

       perf-record(1), perf-script(1)

NOTES         top

        1. addr.dso@addr.offset

        2. dso@symbol

COLOPHON         top

       This page is part of the perf (Performance analysis tools for Linux
       (in Linux source tree)) project.  Information about the project can
       be found at ⟨⟩.  If
       you have a bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on
       2019-03-06.  (At that time, the date of the most recent commit that
       was found in the repository was 2019-03-05.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

perf                             03/06/2019                    PERF-TRACE(1)

Pages that refer to this page: perf-ftrace(1)perf-probe(1)strace(1)