Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751935AbZIHTBG (ORCPT ); Tue, 8 Sep 2009 15:01:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751638AbZIHTBG (ORCPT ); Tue, 8 Sep 2009 15:01:06 -0400 Received: from srv5.dvmed.net ([207.36.208.214]:39417 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751548AbZIHTBF (ORCPT ); Tue, 8 Sep 2009 15:01:05 -0400 Message-ID: <4AA6A9E8.9000407@garzik.org> Date: Tue, 08 Sep 2009 15:00:56 -0400 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Thunderbird/3.0b3 MIME-Version: 1.0 To: Jesse Brandeburg CC: Serge Belyshev , Ingo Molnar , Con Kolivas , linux-kernel@vger.kernel.org, Peter Zijlstra , Mike Galbraith Subject: Re: Epic regression in throughput since v2.6.23 References: <20090906205952.GA6516@elte.hu> <87hbvdiogq.fsf@depni.sinp.msu.ru> <4807377b0909081047kfad088j694bd2b806075c5f@mail.gmail.com> In-Reply-To: <4807377b0909081047kfad088j694bd2b806075c5f@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-Spam-Report: SpamAssassin version 3.2.5 on srv5.dvmed.net summary: Content analysis details: (-4.4 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1253 Lines: 30 On 09/08/2009 01:47 PM, Jesse Brandeburg wrote: > On Tue, Sep 8, 2009 at 5:57 AM, Serge > Belyshev wrote: >> >> Hi. I've done measurments of time taken by make -j4 kernel build >> on a quadcore box. Results are interesting: mainline kernel >> has regressed since v2.6.23 release by more than 10%. > > Is this related to why I now have to double the amount of threads X I > pass to make -jX, in order to use all my idle time for a kernel > compile? I had noticed (without measuring exactly) that it seems with > each kernel released in this series mentioned, I had to increase my > number of worker threads, my common working model now is (cpus * 2) in > order to get zero idle time. You will almost certainly see idle CPUs/threads with "make -jN_CPUS" due to processes waiting for I/O. If you're curious, there is also room for experimenting with make's "-l" argument, which caps the number of jobs based on load average rather than a static number of job slots. Jeff -- 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/