Hello Namhyung, On Thu, Dec 19, 2024 at 10:34 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > This option is to implement the event sampling for system calls in BPF. > When it's used, it picks up a syscall in the given sampling period and > discard others. The period is in msec as it shows the time in msec. > > # perf trace -C 0 --syscall-sample 100 sleep 1 > ? ( ): fleetspeakd/1828559 ... [continued]: futex()) = -1 ETIMEDOUT (Connection timed out) > 0.050 (100.247 ms): gnome-shell/572531 recvmsg(fd: 10<socket:[3355761]>, msg: 0x7ffef8b39d20) = 40 > 100.357 (100.149 ms): pipewire-pulse/572245 read(fd: 5<anon_inode:[eventfd]>, buf: 0x7ffc0b9dc8f0, count: 8) = 8 > 200.553 (100.268 ms): NetworkManager/3424 epoll_wait(epfd: 19<anon_inode:[eventpoll]>, events: 0x5607b85bb880, maxevents: 6) = 0 > 300.876 ( ): mon/4932 poll(ufds: 0x7fa392784df0, nfds: 1, timeout_msecs: 100) ... > 400.901 ( 0.025 ms): TaskCon~ller #/620145 futex(uaddr: 0x7f3fc596fa00, op: WAKE|PRIVATE_FLAG, val: 1) = 0 > 300.876 (100.123 ms): mon/4932 ... [continued]: poll()) = 0 (Timeout) > 500.901 ( 0.012 ms): evdefer/2/2335122 futex(uaddr: 0x5640baac5198, op: WAKE|PRIVATE_FLAG, val: 1) = 0 > 602.701 ( 0.017 ms): Compositor/1992200 futex(uaddr: 0x7f1a51dfdd40, op: WAKE|PRIVATE_FLAG, val: 1) = 0 > 705.589 ( 0.017 ms): JS Watchdog/947933 futex(uaddr: 0x7f4cac1d4240, op: WAKE|PRIVATE_FLAG, val: 1) = 0 > 812.667 ( 0.027 ms): fix/1985151 futex(uaddr: 0xc0008f7148, op: WAKE|PRIVATE_FLAG, val: 1) = 1 > 912.807 ( 0.017 ms): Xorg/572315 setitimer(value: 0x7ffc375d6ba0) = 0 > > The timestamp is kept in a per-cpu array and the allowed task is saved > in a BPF hash map. For non-BPF use cases, it won't work so an error > message would be displayed. > > # perf trace --syscall-sample 100 sleep 1 > ERROR: --syscall-sample works only for BPF > > Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx> > --- > v2 changes) > * rename to --syscall-sample and update the description > * print error when BPF is not available (Arnaldo) > * rename to sample_period_ns (Ian) Acked-by: Howard Chu <howardchu95@xxxxxxxxx> Thanks, Howard
