Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941218AbcKXS7M (ORCPT ); Thu, 24 Nov 2016 13:59:12 -0500 Received: from merlin.infradead.org ([205.233.59.134]:51994 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935677AbcKXS7L (ORCPT ); Thu, 24 Nov 2016 13:59:11 -0500 Date: Thu, 24 Nov 2016 19:58:49 +0100 From: Peter Zijlstra To: Andi Kleen Cc: "Liang, Kan" , Jiri Olsa , "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" , "Hunter, Adrian" , "wangnan0@huawei.com" , "mark.rutland@arm.com" Subject: Re: [PATCH 01/14] perf/x86: Introduce PERF_RECORD_OVERHEAD Message-ID: <20161124185849.GJ3092@twins.programming.kicks-ass.net> References: <1479894292-16277-1-git-send-email-kan.liang@intel.com> <1479894292-16277-2-git-send-email-kan.liang@intel.com> <20161123234122.GA19783@krava> <37D7C6CF3E00A74B8858931C1DB2F07750CA2BC9@SHSMSX103.ccr.corp.intel.com> <20161124135043.GF3092@twins.programming.kicks-ass.net> <20161124182821.GD26852@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161124182821.GD26852@two.firstfloor.org> 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 Content-Length: 873 Lines: 22 On Thu, Nov 24, 2016 at 10:28:22AM -0800, Andi Kleen wrote: > On Thu, Nov 24, 2016 at 02:50:43PM +0100, Peter Zijlstra wrote: > > On Thu, Nov 24, 2016 at 01:45:28PM +0000, Liang, Kan wrote: > > > > I think we should make this optional/configurable like the rest of the aux > > > > events, like below.. > > > > > > > > > > The overhead logging only happens when event is going to be disabled or > > > the task is scheduling out. It should not be much and expensive. > > > > > > Peter, > > > > > > What do you think? > > > Should we make it configurable? > > > > Is there a downside to having it optional? > > It would be good to always have at least one line overhead summary in the > default output. So if someone sends you a perf report output file and it has > suspicious overhead can investigate. Sure, but that's a tool thing, totally irrelevant for the kernel.