From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753230AbXCMK5w (ORCPT ); Tue, 13 Mar 2007 06:57:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753225AbXCMK5w (ORCPT ); Tue, 13 Mar 2007 06:57:52 -0400 Received: from mx1.suse.de ([195.135.220.2]:54294 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753228AbXCMK5v (ORCPT ); Tue, 13 Mar 2007 06:57:51 -0400 Date: Tue, 13 Mar 2007 11:57:42 +0100 From: Andrea Arcangeli To: Nick Piggin Cc: Anton Blanchard , Rik van Riel , Lorenzo Allegrucci , linux-kernel@vger.kernel.org, Ingo Molnar , Suparna Bhattacharya , Jens Axboe Subject: Re: SMP performance degradation with sysbench Message-ID: <20070313105742.GG8992@v2.random> References: <1172425476.5489.11.camel@odyssey.lan> <45E21FEC.9060605@redhat.com> <45E2E244.8040009@yahoo.com.au> <20070312220042.GA807@kryten> <45F63266.1080509@yahoo.com.au> <20070313094559.GC8992@v2.random> <45F67796.4040508@yahoo.com.au> <20070313103134.GF8992@v2.random> <45F67F02.5020401@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45F67F02.5020401@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 13, 2007 at 09:37:54PM +1100, Nick Piggin wrote: > Well it wasn't iowait time. From Anton's analysis, I would probably > say it was time waiting for either the glibc malloc mutex or MySQL > heap mutex. So it again makes little sense to me that this is idle time, unless some userland mutex has a usleep in the slow path which would be very wrong, in the worst case they should yield() (yield can still waste lots of cpu if two tasks in the slow paths calls it while the holder is not scheduled, but at least it wouldn't be idle time). Idle time is suspicious for a kernel issue in the scheduler or some userland inefficiency (the latter sounds more likely).