From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757307Ab1LWOmk (ORCPT ); Fri, 23 Dec 2011 09:42:40 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:55129 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751418Ab1LWOmi (ORCPT ); Fri, 23 Dec 2011 09:42:38 -0500 Date: Fri, 23 Dec 2011 15:40:40 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Robert Richter , Arnaldo Carvalho de Melo , Stephane Eranian , LKML Subject: Re: [PATCH 4/4] perf script: Add script to collect and display IBS samples Message-ID: <20111223144040.GB2297@elte.hu> References: <1323969824-9711-1-git-send-email-robert.richter@amd.com> <1323969824-9711-5-git-send-email-robert.richter@amd.com> <20111223103329.GC4749@elte.hu> <20111223111958.GE16765@erda.amd.com> <20111223135340.GB21382@elte.hu> <1324649698.24803.55.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1324649698.24803.55.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=AWL,BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] 0.0 AWL AWL: From: address is in the auto white-list Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Fri, 2011-12-23 at 14:53 +0100, Ingo Molnar wrote: > > * Robert Richter wrote: > > > > > > Also, could you quote example output of "perf script report > > > > ibs"? > > > > > > IBS_FETCH sample on cpu6 IBS0: 0x00170003186a186a IBS1: 0x0000000000444780 IBS2:0x000000041af26780 > > > IBS_FETCH sample on cpu6 IBS0: 0x00170003186a186a IBS1: 0x00007f5efb44e3b2 IBS2:0x000000042fcff3b2 > > > IBS_FETCH sample on cpu6 IBS0: 0x01370003186a186a IBS1: 0xffffffff81065273 IBS2:0x0000000001065273 > > > IBS_FETCH sample on cpu6 IBS0: 0x01370003186a186a IBS1: 0xffffffff811a6320 IBS2:0x00000000011a6320 > > > IBS_FETCH sample on cpu6 IBS0: 0x01370003186a186a IBS1: 0xffffffff81065255 IBS2:0x0000000001065255 > > > IBS_FETCH sample on cpu7 IBS0: 0x00170004186a186a IBS1: 0x00007fbf0c687ca0 IBS2:0x000000041d345ca0 > > > IBS_FETCH sample on cpu7 IBS0: 0x00170003186a186a IBS1: 0x000000000043bb80 IBS2:0x000000041c351b80 > > > IBS_FETCH sample on cpu7 IBS0: 0x01370003186a186a IBS1: 0xffffffff813d5790 IBS2:0x00000000013d5790 > > > IBS_FETCH sample on cpu7 IBS0: 0x00030001186a186a IBS1: 0xffffffff8102bd00 IBS2:0x00000000013d5d00 > > > > That does not look very usable to users. So why should we merge > > this new ABI in its incomplete form with no complete usecase? > > Being usable is clearly not outside the scope of a new feature > > ... > > > > Integrating it into perf report should not be *that* hard, > > you've done most of the hard work already. But without that > > step we just don't know how complete and usable the whole > > thing is. > > perf annotate like output might make more sense for IBS, maybe > not decode all the information that's in there, but at least a > number of the most useful measurements for each type and > present multiple columns in front of the instructions. > > Ingo, the trouble with IBS is that it doesn't measure > something, its a measure everything together like thing, so > what particular part of this massive bulk data do you use to > create your histograms? My point is that a useful angle to it has to be presented for it to be useful for upstream. The bit that looks useful about IBS is skid-free sampling. So as long as the 'bulk data' contains enough information to do a 'perf record -e instructions:p' work-alike thing it would be useful, right? Sadly precise cycles sampling is not possible via IBS, right? Thanks, Ingo [*] Sidenote: i suspect the RIP+1 sampling artifact cannot be gotten rid of on AMD CPUs, right?