From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: Perf event for Wall-time based sampling? Date: Fri, 19 Sep 2014 08:17:47 -0600 Message-ID: <541C3B0B.3030706@gmail.com> References: <2221771.b2oSN5LR6X@milian-kdab2> <2297882.Vc1x1zOfA6@milian-kdab2> <20140918155745.GH2770@kernel.org> <45528931.El8SOGvs6Z@milian-kdab2> <20140918191713.GK2770@kernel.org> <541B3DED.1010306@gmail.com> <20140918203625.GM2770@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pa0-f49.google.com ([209.85.220.49]:55781 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757146AbaISORu (ORCPT ); Fri, 19 Sep 2014 10:17:50 -0400 Received: by mail-pa0-f49.google.com with SMTP id lf10so196376pab.22 for ; Fri, 19 Sep 2014 07:17:49 -0700 (PDT) In-Reply-To: <20140918203625.GM2770@kernel.org> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Arnaldo Carvalho de Melo Cc: Milian Wolff , linux-perf-users , Namhyung Kim , Ingo Molnar , Joseph Schuchart On 9/18/14, 2:36 PM, Arnaldo Carvalho de Melo wrote: > Ok, so you want to see what is the wait channel and unwind the stack > from there? Is that the case? I.e. again, a sysrq-t equivalent? > >> Milian want is to grab samples every timer expiration even if process is not >> running. > > What for? And by "grab samples" you want to know where it is waiting for > something, together with its callchain? > >> Any limitations that would prevent doing this with a sw event? e.g, mimic >> task-clock just don't disable the timer when the task is scheduled out. > > I'm just trying to figure out if what people want is a complete > backtrace of all threads in a process, no matter what they are doing, at > some given time, i.e. at "sysrq-t" time, is that the case? This has been discussed before: http://thread.gmane.org/gmane.linux.kernel/1307306 Example on the perf wiki: https://perf.wiki.kernel.org/index.php/Tutorial#Profiling_sleep_times David