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. 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
