From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 3/3] perf events: add timehist option to record and report Date: Fri, 18 Feb 2011 19:39:59 +0100 Message-ID: <1298054399.5226.779.camel@laptop> References: <1298008433-22911-1-git-send-email-daahern@cisco.com> <1298008433-22911-4-git-send-email-daahern@cisco.com> <20110218070657.GA11404@elte.hu> <4D5E8204.2090501@cisco.com> <20110218175926.GA3445@nowhere> <4D5EB564.6030504@cisco.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from casper.infradead.org ([85.118.1.10]:55194 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751272Ab1BRSip (ORCPT ); Fri, 18 Feb 2011 13:38:45 -0500 Received: from j77219.upc-j.chello.nl ([24.132.77.219] helo=dyad.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.72 #1 (Red Hat Linux)) id 1PqVE4-0005s3-4s for linux-perf-users@vger.kernel.org; Fri, 18 Feb 2011 18:38:44 +0000 In-Reply-To: <4D5EB564.6030504@cisco.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: David Ahern Cc: Frederic Weisbecker , Ingo Molnar , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, acme@ghostprotocols.net, paulus@samba.org, Thomas Gleixner , Arnaldo Carvalho de Melo On Fri, 2011-02-18 at 11:07 -0700, David Ahern wrote: > We want not only context-switch events, but the stack trace at the > switch. Both ftrace and perf can do that: perf record -ge sched:sched_switch -c 1 or echo 1 > /debug/tracing/options/stacktrace > That data along with the gettimeofday timestamp has allowed us to > resolve performance issues such as a system call taking longer than > expected during a specific sequence of events or a process getting > preempted and not scheduled for N seconds. etc., etc. Non of that seems to require GTOD stamps.