perf-trace man page
perf-trace — strace inspired tool
perf trace perf trace record
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.
- -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. 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.
Filter out events for these pids and for trace itself (comma separated list).
- -v, --verbose=
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 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.
-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=[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 dwarf.
Show the kernel callchains on the syscall exit path.
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.
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.
When tracing pagefaults, the format of the trace is as follows:
<min|maj>fault [<ip.symbol>+<ip.offset>] ⇒ <email@example.com> (<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+offset.
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.