On Mon, Jul 7, 2014 at 12:16 PM, Brendan Gregg <brendan.d.gr...@gmail.com> wrote: > On Mon, Jul 7, 2014 at 12:00 PM, Brendan Gregg > <brendan.d.gr...@gmail.com> wrote: >> On Mon, Jul 7, 2014 at 11:44 AM, David Ahern <dsah...@gmail.com> wrote: >>> On 7/7/14, 12:38 PM, Brendan Gregg wrote: >>>> >>>> G'Day perf users, >>>> >>>> Is there a way to filter perf from tracing itself? >>>> >>>> Here's an idle system: >>>> >>>> # ./perf record -e syscalls:sys_enter_read -a sleep 5 >>>> [ perf record: Woken up 2 times to write data ] >>>> [ perf record: Captured and wrote 0.569 MB perf.data (~24864 samples) ] >>>> # ./perf record -e syscalls:sys_enter_write -a sleep 5 >>>> [ perf record: Woken up 0 times to write data ] >>>> [ perf record: Captured and wrote 150.381 MB perf.data (~6570251 samples) >>>> ] >>>> >>>> Note the disparity. perf is capturing its own writes, creating a feedback >>>> loop. >>> >>> >>> Not a filter, but works around the problem using mmap'ed output file: >>> >>> https://github.com/dsahern/linux/commit/ae2d7010256f5a5b247fb4df9f764a911a34a2f3 >>> >> >> Ah, thanks David, that should work! Looking forward to having this >> patch included. >> > > While this should help a lot of cases, I realized I am using stdout > from time to time as well (similar to the "perf script" framework), > where I don't think mmap() is going to work. Eg: > > # perf record -e raw_syscalls:sys_enter -a -o - sleep 5 | perf script > -i - | stuff... > > Maybe perf should skip itself by-default, unless asked (eg, -I to > include perf's own events). Or some way to filter it would also work, > eg, common_ppid.
I figured out one workaround...: # sh -c 'exec ./perf record -e syscalls:sys_enter_write --filter "common_pid != "$$ -a sleep 5' [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.161 MB perf.data (~7051 samples) ] Brendan -- http://www.brendangregg.com -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
