From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756527AbYKDQpF (ORCPT ); Tue, 4 Nov 2008 11:45:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751064AbYKDQoz (ORCPT ); Tue, 4 Nov 2008 11:44:55 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:54576 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751007AbYKDQoy (ORCPT ); Tue, 4 Nov 2008 11:44:54 -0500 Date: Tue, 4 Nov 2008 17:43:58 +0100 From: Ingo Molnar To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Andrew Morton , Steven Rostedt Subject: Re: [PATCH 3/3] ftrace: function tracer with irqs disabled Message-ID: <20081104164358.GB27339@elte.hu> References: <20081104041554.605521183@goodmis.org> <20081104042203.499871423@goodmis.org> <20081104080747.GA27075@elte.hu> <20081104090405.GA507@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00,DNS_FROM_SECURITYSAGE autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 0.0 DNS_FROM_SECURITYSAGE RBL: Envelope sender in blackholes.securitysage.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt wrote: > > > > tracing type times entries recorded > > > > ------------ -------- ---------------- > > > > irq disabled 43.393 166433066 > > > > 43.282 166172618 > > > > 43.298 166256704 > > > > > > > > preempt disabled 38.969 159871710 > > > > 38.943 159972935 > > > > 39.325 161056510 > When we used the preempt disabled version, we lost 5 million traces, > as suppose to the irq disabled which was only 1,150 traces lost. > > Considering that we had 166,256,704 traces total, that 5 million is > only 4% lost of traces. Still quite a lot. But again, this is an > extreme, because we are tracing hackbench. there's about 10% difference between the two hackbench results - so the lack of 5% of the traces could make up for about half of that overhead. anyway, that still leaves the other 5% as the _true_ overhead of IRQ disable. is there some other workload that does not lose this many trace entries, making it easier to compare irqs-off against preempt-off? Ingo