Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754147AbYKJVo2 (ORCPT ); Mon, 10 Nov 2008 16:44:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751188AbYKJVoU (ORCPT ); Mon, 10 Nov 2008 16:44:20 -0500 Received: from out5.smtp.messagingengine.com ([66.111.4.29]:46846 "EHLO out5.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973AbYKJVoT (ORCPT ); Mon, 10 Nov 2008 16:44:19 -0500 Message-Id: <1226353458.27999.1284030023@webmail.messagingengine.com> X-Sasl-Enc: hq/BB8pZkdREw9HxIK8j9h7Lf4skjSg+RnZZqw3s9Cid 1226353458 From: "Alexander van Heukelum" To: "H. Peter Anvin" , "Ingo Molnar" Cc: "Andi Kleen" , "Cyrill Gorcunov" , "Alexander van Heukelum" , "LKML" , "Thomas Gleixner" , lguest@ozlabs.org, jeremy@xensource.com, "Steven Rostedt" , "Mike Travis" Content-Disposition: inline Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 X-Mailer: MessagingEngine.com Webmail Interface References: <20081104122839.GA22864@mailshack.com> <20081104150729.GC21470@localhost> <20081104170501.GE29626@one.firstfloor.org> <1225822006.21441.1282961299@webmail.messagingengine.com> <20081104204400.GC10825@elte.hu> <1226243805.27361.1283784629@webmail.messagingengine.com> <20081110085846.GG22392@elte.hu> <491855AA.5060100@zytor.com> Subject: Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes In-Reply-To: <491855AA.5060100@zytor.com> Date: Mon, 10 Nov 2008 22:44:18 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1829 Lines: 47 On Mon, 10 Nov 2008 07:39:22 -0800, "H. Peter Anvin" said: > Ingo Molnar wrote: > > * Alexander van Heukelum wrote: > > > > hackbench is _way_ too noisy to measure such cycle-level differences > > as irq entry changes cause. It also does not really stress interrupts > > - it only stresses networking, the VFS and the scheduler. > > > > a better test might have been to generate a ton of interrupts, but > > even then it's _very_ hard to measure it properly. The best method is > > what i've suggested to you early on: run a loop in user-space and > > observe irq costs via RDTSC, as they happen. Then build a histogram > > and compare the before/after histogram. Compare best-case results as > > well (the first slot of the histogram), as those are statistically > > much more significant than a noisy average. > > > > For what it's worth, I tested this out, and I'm pretty sure you need to > run a uniprocessor configuration (or system) for it to make sense -- > otherwise you end up missing too many of the interrupts. I first tested > this on an 8-processor system and, well, came up with nothing. > > I'm going to try this later on a uniprocessor, unless Alexander beats me > to it. I did the rdtsctest again for the irqstubs patch you sent. The data is at http://heukelum.fastmail.fm/irqstubs/ and the latency histogram is http://heukelum.fastmail.fm/irqstubs/latency_hpa.png Greetings, Alexander > -hpa -- Alexander van Heukelum heukelum@fastmail.fm -- http://www.fastmail.fm - Same, same, but different... -- 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/