From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754015AbZBAKEg (ORCPT ); Sun, 1 Feb 2009 05:04:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752682AbZBAKE1 (ORCPT ); Sun, 1 Feb 2009 05:04:27 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:39595 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752618AbZBAKE0 (ORCPT ); Sun, 1 Feb 2009 05:04:26 -0500 Date: Sun, 1 Feb 2009 11:04:10 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Lin Ming , "Zhang, Yanmin" , linux-kernel Subject: Re: hackbench [pthread mode] regression with 2.6.29-rc3 Message-ID: <20090201100410.GA22903@elte.hu> References: <1233473426.2604.13.camel@ymzhang> <1233476961.13659.12.camel@minggr.sh.intel.com> <1233479836.4787.63.camel@laptop> <1233482239.4787.65.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1233482239.4787.65.camel@laptop> 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 * Peter Zijlstra wrote: > On Sun, 2009-02-01 at 10:17 +0100, Peter Zijlstra wrote: > > On Sun, 2009-02-01 at 16:29 +0800, Lin Ming wrote: > > > > Bisect located below patch. > > > > commit 490dea45d00f01847ebebd007685d564aaf2cd98 > > > > Author: Peter Zijlstra > > > > Date: Mon Nov 24 17:06:57 2008 +0100 > > > > > > > > itimers: remove the per-cpu-ish-ness > > > > > > > > Either we bounce once cacheline per cpu per tick, yielding n^2 bounces > > > > or we just bounce a single.. > > > > > > > > Also, using per-cpu allocations for the thread-groups complicates the > > > > per-cpu allocator in that its currently aimed to be a fixed sized > > > > allocator and the only possible extention to that would be vmap based, > > > > which is seriously constrained on 32 bit archs. > > > > > > > > > > > > After above patch is reverted, hackbench result is restored. > > > > > > oltp has ~3% regression with 2.6.29-rc3 on 4core*2p stokley machine. > > > After above patch reverted, the regression disappeared. > > > > *sigh*, did they gain anything with introduction of the per-cpu crap? > > No it wouldn't have, I just missed something obvious,.. :-( > > I wish we never merged that crap... oh, it certainly had its use: it highlighted that we have crappy threading+timers code (on hackbench_pth) since the beginning of the Linux SMP times. Ingo