From mboxrd@z Thu Jan 1 00:00:00 1970 From: William Cohen Subject: Re: Fwd: filtering perf itself Date: Tue, 08 Jul 2014 15:10:53 -0400 Message-ID: <53BC423D.7040208@redhat.com> References: <53BAEA99.7050602@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:52016 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754835AbaGHTK5 (ORCPT ); Tue, 8 Jul 2014 15:10:57 -0400 In-Reply-To: Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Brendan Gregg , David Ahern Cc: linux-perf-users@vger.kernel.org On 07/07/2014 03:00 PM, Brendan Gregg wrote: > On Mon, Jul 7, 2014 at 11:44 AM, David Ahern 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? -Will >> >> 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. > > Brendan >