Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965786AbcKXO2V (ORCPT ); Thu, 24 Nov 2016 09:28:21 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49686 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965607AbcKXO2T (ORCPT ); Thu, 24 Nov 2016 09:28:19 -0500 Date: Thu, 24 Nov 2016 15:27:47 +0100 From: Jiri Olsa To: "Liang, Kan" Cc: Peter Zijlstra , "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" , "andi@firstfloor.org" Subject: Re: [PATCH 01/14] perf/x86: Introduce PERF_RECORD_OVERHEAD Message-ID: <20161124142747.GA30490@krava> 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> <37D7C6CF3E00A74B8858931C1DB2F07750CA2BFE@SHSMSX103.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F07750CA2BFE@SHSMSX103.ccr.corp.intel.com> User-Agent: Mutt/1.7.1 (2016-10-04) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 24 Nov 2016 14:27:52 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1095 Lines: 37 On Thu, Nov 24, 2016 at 01:56:51PM +0000, Liang, Kan 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? > > NO. There will be no overhead information dumped into perf.data. Just like > current implementation. old perf tools will get unexpected events if it's not optional [root@ibm-x3650m4-01 perf]# ./perf c2c record -ag ^C[ perf record: Woken up 1 times to write data ] Warning: Found 1 unknown events! Is this an older tool processing a perf.data file generated by a more recent tool? If that is not the case, consider reporting to linux-kernel@vger.kernel.org. [ perf record: Captured and wrote 2.333 MB perf.data (9370 samples) ] jirka