G'Day Will, On Tue, Jul 8, 2014 at 12:10 PM, William Cohen <wco...@redhat.com> wrote: > On 07/07/2014 03:00 PM, Brendan Gregg 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. >>> > > What about probing using SystemTap and doing filtering in the probe handler > to exclude the monitoring process?
Yes, that works, and in addition I can do custom in-kernel aggregations with SystemTap, which reduces overheads much further. My problem is finding the time to check that 2.6 is safe for production use (I already know that perf_events is). 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
