Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758724Ab1DYRla (ORCPT ); Mon, 25 Apr 2011 13:41:30 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40478 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758664Ab1DYRl3 (ORCPT ); Mon, 25 Apr 2011 13:41:29 -0400 Date: Mon, 25 Apr 2011 19:41:10 +0200 From: Ingo Molnar To: Andi Kleen Cc: Peter Zijlstra , arun@sharma-home.net, Stephane Eranian , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Lin Ming , Arnaldo Carvalho de Melo , Thomas Gleixner , eranian@gmail.com, Arun Sharma , Linus Torvalds , Andrew Morton Subject: Re: [generalized cache events] Re: [PATCH 1/1] perf tools: Add missing user space support for config1/config2 Message-ID: <20110425174110.GB28239@elte.hu> References: <20110422092322.GA1948@elte.hu> <20110422105211.GB1948@elte.hu> <20110422165007.GA18401@vps.sharma-home.net> <20110422203022.GA20573@elte.hu> <20110422203222.GA21219@elte.hu> <20110423000347.GC9328@tassilo.jf.intel.com> <1303545012.2298.44.camel@twins> <20110424021907.GB3019@alboin.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110424021907.GB3019@alboin.amr.corp.intel.com> User-Agent: Mutt/1.5.20 (2009-08-17) 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=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1291 Lines: 33 * Andi Kleen wrote: > > You're so skilled at not actually saying anything useful. Are you > > perchance referring to the fact that the IP reported in the PEBS data is > > exactly _one_ instruction off? Something that is demonstrated to be > > fixable? > > It's one instruction off the instruction that was retired when the PEBS > interrupt was ready, but not one instruction off the instruction that caused > the event. There's still skid in triggering the interrupt. Peter answered this in the other mail: | | Sure, but who cares? So your period isn't exactly what you specified, but | the effective period will have an average and a fairly small stdev (assuming | the initial period is much larger than the relatively few cycles it takes to | arm the PEBS assist), therefore you still get a fairly uniform spread. | ... and the resulting low level of noise in the average period length is what matters. The instruction itself will still be one of the hotspot instructions, statistically. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/