Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754220AbYK2T7c (ORCPT ); Sat, 29 Nov 2008 14:59:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752308AbYK2T7Y (ORCPT ); Sat, 29 Nov 2008 14:59:24 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:37203 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752244AbYK2T7X (ORCPT ); Sat, 29 Nov 2008 14:59:23 -0500 Date: Sat, 29 Nov 2008 20:58:36 +0100 From: Ingo Molnar To: Avi Kivity Cc: Alexander van Heukelum , "H. Peter Anvin" , Alexander van Heukelum , lguest@ozlabs.org, jeremy@xensource.com, LKML , Mike Travis , Cyrill Gorcunov , Steven Rostedt , Andi Kleen , Thomas Gleixner Subject: Re: [Lguest] [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes Message-ID: <20081129195836.GA27836@elte.hu> References: <1225822006.21441.1282961299@webmail.messagingengine.com> <20081104204400.GC10825@elte.hu> <1226243805.27361.1283784629@webmail.messagingengine.com> <49178E89.2000307@zytor.com> <492DC13F.8020009@redhat.com> <492DE3EF.8060507@zytor.com> <492E72D7.9060201@redhat.com> <20081128204809.GA17920@mailshack.com> <20081129154516.GA26579@mailshack.com> <49318871.8010501@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49318871.8010501@redhat.com> 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 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian 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: 1389 Lines: 31 * Avi Kivity wrote: > Alexander van Heukelum wrote: >> I now did the benchmarks for the same -rc6 with hpa's 4-byte stubs >> too. Same machine. It's significantly better than the other two >> options in terms of speed. It takes about 7% less cpu to handle >> the interrupts. (0.64% cpu instead of 0.69%.) I have to run now, >> I'll let interpreting the histogram to someone else ;). >> > > This is noise. 0.05% cpu on a 1GHz machine servicing 1000 interrupt/sec > boils down to 500 cycles/interrupt. These changes shouldn't amount to > so much (and I doubt you have 1000 interrupts/sec with a single disk).. > > I'm sorry, but the whole effort is misguided, in my opinion. If you > want to optimize, try reducing the number of interrupts that occur > rather than saving a few cycles in the interrupt path. the goal was not to optimize those workloads - the goal was to (try to) validate those irq trampoline changes / cleanups. We went with hpa's changes in the end which compresses the trampolines - that reduces the $icache footprint which is hard to measure but a very real concern on real workloads. 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/