Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758048AbYCYQOR (ORCPT ); Tue, 25 Mar 2008 12:14:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756203AbYCYQOE (ORCPT ); Tue, 25 Mar 2008 12:14:04 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:39862 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755969AbYCYQOD (ORCPT ); Tue, 25 Mar 2008 12:14:03 -0400 Subject: Re: Scalability requirements for sysv ipc From: Peter Zijlstra To: Mike Galbraith Cc: Manfred Spraul , Linux Kernel Mailing List , paulmck@linux.vnet.ibm.com, Nadia Derbey , Andrew Morton , Ingo Molnar In-Reply-To: <1206460206.4414.21.camel@marge.simson.net> References: <47E382DB.70503@colorfullife.com> <47E3ADE3.4030304@bull.net> <47E3B924.3000304@colorfullife.com> <20080321141339.GB9618@linux.vnet.ibm.com> <47E3DD8C.4000904@colorfullife.com> <1206164608.3659.11.camel@marge.simson.net> <47E4DB06.3020003@colorfullife.com> <1206186832.4545.1.camel@marge.simson.net> <47E51637.8060102@colorfullife.com> <47E55945.10109@colorfullife.com> <1206460206.4414.21.camel@marge.simson.net> Content-Type: text/plain Date: Tue, 25 Mar 2008 17:13:50 +0100 Message-Id: <1206461630.8514.441.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.21.92 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2320 Lines: 48 On Tue, 2008-03-25 at 16:50 +0100, Mike Galbraith wrote: > On Sat, 2008-03-22 at 20:08 +0100, Manfred Spraul wrote: > > > just the normal performance of 2.6.25-rc3 is abyssimal, 55 to 60% slower > > than 2.6.18.8: > > After manually reverting 3e148c79938aa39035669c1cfa3ff60722134535, > 2.6.25.git scaled linearly, but as you noted, markedly down from earlier > kernels with this benchmark. 2.6.24.4 with same revert, but all > 2.6.25.git ipc changes piled on top still performed close to 2.6.22, so > I went looking. Bisection led me to.. > > 8f4d37ec073c17e2d4aa8851df5837d798606d6f is first bad commit > commit 8f4d37ec073c17e2d4aa8851df5837d798606d6f > Author: Peter Zijlstra > Date: Fri Jan 25 21:08:29 2008 +0100 > > sched: high-res preemption tick > > Use HR-timers (when available) to deliver an accurate preemption tick. > > The regular scheduler tick that runs at 1/HZ can be too coarse when nice > level are used. The fairness system will still keep the cpu utilisation 'fair' > by then delaying the task that got an excessive amount of CPU time but try to > minimize this by delivering preemption points spot-on. > > The average frequency of this extra interrupt is sched_latency / nr_latency. > Which need not be higher than 1/HZ, its just that the distribution within the > sched_latency period is important. > > Signed-off-by: Peter Zijlstra > Signed-off-by: Ingo Molnar > > :040000 040000 ab225228500f7a19d5ad20ca12ca3fc8ff5f5ad1 f1742e1d225a72aecea9d6961ed989b5943d31d8 M arch > :040000 040000 25d85e4ef7a71b0cc76801a2526ebeb4dce180fe ae61510186b4fad708ef0211ac169decba16d4e5 M include > :040000 040000 9247cec7dd506c648ac027c17e5a07145aa41b26 950832cc1dc4d30923f593ecec883a06b45d62e9 M kernel > > ...and I verified it via :-/ echo 7 > sched_features in latest. That > only bought me roughly half though, so there's a part three in there > somewhere. Ouch, I guess hrtimers are just way expensive on some hardware... -- 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/