From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brendan Gregg Subject: Re: Fwd: filtering perf itself Date: Mon, 7 Jul 2014 12:00:52 -0700 Message-ID: References: <53BAEA99.7050602@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-qg0-f49.google.com ([209.85.192.49]:41863 "EHLO mail-qg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750859AbaGGTAy (ORCPT ); Mon, 7 Jul 2014 15:00:54 -0400 Received: by mail-qg0-f49.google.com with SMTP id f51so3969581qge.22 for ; Mon, 07 Jul 2014 12:00:54 -0700 (PDT) In-Reply-To: <53BAEA99.7050602@gmail.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: David Ahern Cc: linux-perf-users@vger.kernel.org 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. > > > 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 -- http://www.brendangregg.com