Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752201AbZIHUeI (ORCPT ); Tue, 8 Sep 2009 16:34:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751688AbZIHUeI (ORCPT ); Tue, 8 Sep 2009 16:34:08 -0400 Received: from brick.kernel.dk ([93.163.65.50]:44902 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089AbZIHUeH (ORCPT ); Tue, 8 Sep 2009 16:34:07 -0400 Date: Tue, 8 Sep 2009 22:34:10 +0200 From: Jens Axboe To: Peter Zijlstra Cc: Ingo Molnar , Con Kolivas , linux-kernel@vger.kernel.org, Mike Galbraith Subject: Re: BFS vs. mainline scheduler benchmarks and measurements Message-ID: <20090908203409.GJ18599@kernel.dk> References: <20090906205952.GA6516@elte.hu> <20090907094953.GP18599@kernel.dk> <20090907115750.GW18599@kernel.dk> <20090907141458.GD24507@elte.hu> <20090907173846.GB18599@kernel.dk> <20090907204458.GJ18599@kernel.dk> <20090908091304.GQ18599@kernel.dk> <1252423398.7746.97.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1252423398.7746.97.camel@twins> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1335 Lines: 33 On Tue, Sep 08 2009, Peter Zijlstra wrote: > On Tue, 2009-09-08 at 11:13 +0200, Jens Axboe wrote: > > And here's a newer version. > > I tinkered a bit with your proglet and finally found the problem. > > You used a single pipe per child, this means the loop in run_child() > would consume what it just wrote out until it got force preempted by the > parent which would also get woken. > > This results in the child spinning a while (its full quota) and only > reporting the last timestamp to the parent. Oh doh, that's not well thought out. Well it was a quick hack :-) Thanks for the fixup, now it's at least usable to some degree. > Since consumer (parent) is a single thread the program basically > measures the worst delay in a thundering herd wakeup of N children. Yes, it's really meant to measure how long it takes to wake a group of processes, assuming that this is where things fall down on the 'box loaded, switch desktop' case. Now whether that's useful or not or whether this test app is worth the bits it takes up on the hard drive, is another question. -- Jens Axboe -- 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/