From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965089AbWDNBRU (ORCPT ); Thu, 13 Apr 2006 21:17:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965090AbWDNBRU (ORCPT ); Thu, 13 Apr 2006 21:17:20 -0400 Received: from omta01ps.mx.bigpond.com ([144.140.82.153]:58976 "EHLO omta01ps.mx.bigpond.com") by vger.kernel.org with ESMTP id S965089AbWDNBRT (ORCPT ); Thu, 13 Apr 2006 21:17:19 -0400 Message-ID: <443EF81C.9020800@bigpond.net.au> Date: Fri, 14 Apr 2006 11:17:16 +1000 From: Peter Williams User-Agent: Thunderbird 1.5 (X11/20060313) MIME-Version: 1.0 To: "Siddha, Suresh B" CC: Andrew Morton , "Chen, Kenneth W" , Con Kolivas , Ingo Molnar , Mike Galbraith , Nick Piggin , Linux Kernel Mailing List Subject: Re: smpnice: issues with finding busiest queue References: <4439FF0C.8030407@bigpond.net.au> <20060410181237.A26977@unix-os.sc.intel.com> <443C3FD8.2060906@bigpond.net.au> <20060411185709.A2401@unix-os.sc.intel.com> <443C8AEC.9010309@bigpond.net.au> <443D95DF.2090807@bigpond.net.au> <20060413173104.B15723@unix-os.sc.intel.com> In-Reply-To: <20060413173104.B15723@unix-os.sc.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Authentication-Info: Submitted using SMTP AUTH PLAIN at omta01ps.mx.bigpond.com from [147.10.133.38] using ID pwil3058@bigpond.net.au at Fri, 14 Apr 2006 01:17:17 +0000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Siddha, Suresh B wrote: > On Thu, Apr 13, 2006 at 10:05:51AM +1000, Peter Williams wrote: >> There be dragons here :-(. >> > > At more places in this part of the world (smpnice) :) > > We need to relook at find_busiest_queue()... With the current weighted > calculations, it doesn't always make sense to look at the highest weighted > runqueue in the busy group.. > > for example on a DP with HT system, how does the load balance behave with > Package-0 containing one high priority and one low priority, Package-1 > containing one low priority(with other thread being idle).. > > Package-1 thinks that it need to take the low priority thread from Package-0. > And find_busiest_queue() returns the cpu thread with highest priority task.. > And ultimately(with help of active load balance) we move high priority > task to Package-1. And same continues with Package-0 now, moving high priority > task from package-1 to package-0.. > > Even without the presence of active load balance, load balance will fail > to balance(having two low priority tasks on one package, and high > priority task on another package) the above scenario.... > > We probably need to use imbalance(and more factors) to determine the busiest > queue in the group..... A patch would be nice. -- Peter Williams pwil3058@bigpond.net.au "Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce