From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267418AbUHJEKk (ORCPT ); Tue, 10 Aug 2004 00:10:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267417AbUHJEKk (ORCPT ); Tue, 10 Aug 2004 00:10:40 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.101]:23011 "EHLO e1.ny.us.ibm.com") by vger.kernel.org with ESMTP id S267409AbUHJEK2 (ORCPT ); Tue, 10 Aug 2004 00:10:28 -0400 From: Andrew Theurer To: linux-kernel@vger.kernel.org Subject: Re: 2.6.8-rc2-mm2 performance improvements (scheduler?) Date: Mon, 9 Aug 2004 23:08:56 -0500 User-Agent: KMail/1.5 References: <200408092240.05287.habanero@us.ibm.com> In-Reply-To: <200408092240.05287.habanero@us.ibm.com> Cc: rocklind@us.ibm.com, mbligh@aracnet.com, mingo@elte.hu, akpm@osdl.org MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200408092308.56160.habanero@us.ibm.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 09 August 2004 22:40, you wrote: > Rick showed me schedstats graphs of the two ... it seems to have lower > latency, does less rebalancing, fewer pull_tasks, etc, etc. Everything > looks better ... he'll send them out soon, I think (hint, hint). > > Okay, they're done. Here's the URL of the graphs: > > http://eaglet.rain.com/rick/linux/staircase/scase-vs-noscase.html > > General summary: as Martin reported, we're seeing improvements in a number > of areas, at least with sdet. The graphs as listed there represent stats > from four separate sdet runs run sequentially with an increasing load. > (We're trying to see if we can get the information from each run > separately, rather than the aggregate -- one of the hazards of an automated > test harness :) What's quite interesting is that there is a very noticeable surge in load_balance with staircase in the early stage of the test, but there appears to be -no- direct policy changes to load-balance at all in Con's patch (or at least I didn't notice it -please tell me if you did!). You can see it in busy load_balance, sched_balance_exec, and pull_task. The runslice and latency stats confirm this -no-staircase does not balance early on, and the tasks suffer, waiting on a cpu already loaded up. I do not have an explanation for this; perhaps it has something to do with eliminating expired queue. I would be nice to have per cpu runqueue lengths logged to see how this plays out -do the cpus on staircase obtain a runqueue length close to nr_running()/nr_online_cpus sooner than no-staircase? Also, one big change apparent to me, the elimination of TIMESLICE_GRANULARITY. Do you have cswitch data? I would not be surprised if it's a lot higher on -no-staircase, and cache is thrashed a lot more. This may be something you can pull out of the -no-staircase kernel quite easily. -Andrew Theurer