# perf-trace

## NAME



           perf-trace - strace inspired tool
    


## SYNOPSIS



           _perf trace_
           _perf trace record_
    


## DESCRIPTION



           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 perf.data
           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



           -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.
    
           --filter=<filter>
               Event filter. This option should follow an event selector (-e)
               which selects tracepoint event(s).
    
           -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-pids=
               Filter out events for these pids and for _trace_ itself (comma
               separated list).
    
           -v, --verbose
               Increase the verbosity level.
    
           --no-inherit
               Child tasks do not inherit counters.
    
           -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.
    
           -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 CPUs.
    
           --duration
               Show only events that had a duration greater than N.M ms.
    
           --sched
               Accrue thread runtime and provide a summary at the end of the
               session.
    
           --failure
               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.
    
           --comm
               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.
    
           --errno-summary
               To be used with -s or -S, to show stats for the errnos
               experienced by syscalls, using only this option will trigger
               --summary.
    
           --summary-mode=mode
               To be used with -s or -S, to select how to show summary. By
               default it’ll show the syscall summary by thread. Possible
               values are: thread, total, cgroup.
    
           --tool_stats
               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.
    
           --syscalls
               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 dwarf_.
    
                   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.
    
           --kernel-syscall-graph
               Show the kernel callchains on the syscall exit path.
    
           --max-events=N
               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.
    
           --switch-on EVENT_NAME
               Only consider events after this event is found.
    
           --switch-off EVENT_NAME
               Stop considering events after this event is found.
    
           --show-on-off-events
               Show the --switch-on/off events too.
    
           --max-stack
               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.
    
           --min-stack
               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-sample
               Print the PERF_RECORD_SAMPLE PERF_SAMPLE_ info for the
               raw_syscalls:sys_{enter,exit} tracepoints, for debugging.
    
           --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.
    
           --sort-events
               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.
    
           --libtraceevent_print
               Use libtraceevent to print tracepoint arguments. By default
               _perf trace_ uses the same beautifiers used in the strace-like
               enter+exit lines to augment the tracepoint arguments.
    
           --force-btf
               Use btf_dump to pretty print syscall argument data, instead of
               using hand-crafted pretty printers. This option is intended
               for testing BTF integration in perf trace. btf_dump-based
               pretty-printing serves as a fallback to hand-crafted pretty
               printers, as the latter can better pretty-print integer flags
               and struct pointers.
    
           --bpf-summary
               Collect system call statistics in BPF. This is only for live
               mode and works well with -s/--summary option where no argument
               information is required.
    


## PAGEFAULTS



           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 maps;
    
           •   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
           **dso@symbol******[2]+offset.


## EXAMPLES



           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/libcrypto.so.1.0.0@0x61be0 (x.)
    
               As you can see, there was major pagefault in python process, from
               CRYPTO_push_info_ routine which faulted somewhere in libcrypto.so.
    
           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/ld.so.cache, 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/libxul.so)
                                                    js::gc::Chunk::allocateArena (/usr/lib64/firefox/libxul.so)
                                                    js::gc::GCRuntime::allocateArena (/usr/lib64/firefox/libxul.so)
                                                    js::gc::ArenaLists::allocateFromArena (/usr/lib64/firefox/libxul.so)
                                                    js::gc::GCRuntime::tryNewTenuredThing<JSString, (js::AllowGC)1> (inlined)
                                                    js::AllocateString<JSString, (js::AllowGC)1> (/usr/lib64/firefox/libxul.so)
                                                    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/libxul.so)
                                                    [0x18b26e6bc2bd] (/tmp/perf-17136.map)
               #
    
           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 wide:
    
               # 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]
               #
    


## NOTES



            1. addr.dso@addr.offset
               mailto:addr.dso@addr.offset
    
            2. dso@symbol
               mailto:dso@symbol
    


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