From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752998AbcLFLV0 (ORCPT ); Tue, 6 Dec 2016 06:21:26 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:51406 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752298AbcLFLVZ (ORCPT ); Tue, 6 Dec 2016 06:21:25 -0500 Date: Tue, 6 Dec 2016 12:21:07 +0100 From: Peter Zijlstra To: kan.liang@intel.com Cc: mingo@redhat.com, acme@kernel.org, linux-kernel@vger.kernel.org, alexander.shishkin@linux.intel.com, tglx@linutronix.de, namhyung@kernel.org, jolsa@kernel.org, adrian.hunter@intel.com, wangnan0@huawei.com, mark.rutland@arm.com, andi@firstfloor.org Subject: Re: [PATCH V2 02/13] perf/core: output overhead when sched out from context Message-ID: <20161206112107.GK3124@twins.programming.kicks-ass.net> References: <1480713561-6617-1-git-send-email-kan.liang@intel.com> <1480713561-6617-3-git-send-email-kan.liang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1480713561-6617-3-git-send-email-kan.liang@intel.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 02, 2016 at 04:19:10PM -0500, kan.liang@intel.com wrote: > From: Kan Liang > > Outputing every overhead when it happens is very costly. The accumulated > time is more meaningful. So the overhead information should be outputted > at the very end. > > The overhead information is outputted when task is scheduling out or the > event is going to be disabled. Why? The context switch stuff can happen very frequently. Doesn't seem like a good place to add overhead. > The arch specific overhead is outputted in event pmu delete, when Flag > PERF_EF_LOG is set.