From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030195AbWBGWOp (ORCPT ); Tue, 7 Feb 2006 17:14:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965161AbWBGWOo (ORCPT ); Tue, 7 Feb 2006 17:14:44 -0500 Received: from smtp.osdl.org ([65.172.181.4]:23184 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S965037AbWBGWOo (ORCPT ); Tue, 7 Feb 2006 17:14:44 -0500 Date: Tue, 7 Feb 2006 14:15:25 -0800 From: Andrew Morton To: Con Kolivas Cc: npiggin@suse.de, mingo@elte.hu, rostedt@goodmis.org, pwil3058@bigpond.net.au, suresh.b.siddha@intel.com, linux-kernel@vger.kernel.org, torvalds@osdl.org Subject: Re: [rfc][patch] sched: remove smpnice Message-Id: <20060207141525.19d2b1be.akpm@osdl.org> In-Reply-To: <200602080157.07823.kernel@kolivas.org> References: <20060207142828.GA20930@wotan.suse.de> <200602080157.07823.kernel@kolivas.org> X-Mailer: Sylpheed version 1.0.0 (GTK+ 1.2.10; i386-vine-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Con Kolivas wrote: > > On Wednesday 08 February 2006 01:28, Nick Piggin wrote: > > I'd like to get some comments on removing smpnice for 2.6.16. I don't > > think the code is quite ready, which is why I asked for Peter's additions > > to also be merged before I acked it (although it turned out that it still > > isn't quite ready with his additions either). > > > > Basically I have had similar observations to Suresh in that it does not > > play nicely with the rest of the balancing infrastructure (and raised > > similar concerns in my review). > > > > The samples (group of 4) I got for "maximum recorded imbalance" on a 2x2 > > > > SMP+HT Xeon are as follows: > > | Following boot | hackbench 20 | hackbench 40 > > > > -----------+----------------+---------------------+--------------------- > > 2.6.16-rc2 | 30,37,100,112 | 5600,5530,6020,6090 | 6390,7090,8760,8470 > > +nosmpnice | 3, 2, 4, 2 | 28, 150, 294, 132 | 348, 348, 294, 347 > > > > Hackbench raw performance is down around 15% with smpnice (but that in > > itself isn't a huge deal because it is just a benchmark). However, the > > samples show that the imbalance passed into move_tasks is increased by > > about a factor of 10-30. I think this would also go some way to > > explaining latency blips turning up in the balancing code (though I > > haven't actually measured that). > > > > We'll probably have to revert this in the SUSE kernel. > > > > The other option for 2.6.16 would be to fast track Peter's stuff, which > > I could put some time into... but that seems a bit risky at this stage > > of the game. > > > > I'd like to hear any other suggestions though. Patch included to aid > > discussion at this stage, rather than to encourage any rash decisions. > > I see the demonstrable imbalance but I was wondering if there is there a real > world benchmark that is currently affected? > Well was any real-world workload (or benchmark) improved by the smpnice change? Because if we have one workload which slowed and and none which sped up, it's a pretty easy decision..