Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757963Ab3GRJck (ORCPT ); Thu, 18 Jul 2013 05:32:40 -0400 Received: from merlin.infradead.org ([205.233.59.134]:58121 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757566Ab3GRJci (ORCPT ); Thu, 18 Jul 2013 05:32:38 -0400 Date: Thu, 18 Jul 2013 11:32:18 +0200 From: Peter Zijlstra To: Jason Low Cc: Rik van Riel , Ingo Molnar , LKML , Mike Galbraith , Thomas Gleixner , Paul Turner , Alex Shi , Preeti U Murthy , Vincent Guittot , Morten Rasmussen , Namhyung Kim , Andrew Morton , Kees Cook , Mel Gorman , aswin@hp.com, scott.norton@hp.com, chegu_vinod@hp.com Subject: Re: [RFC] sched: Limit idle_balance() when it is being used too frequently Message-ID: <20130718093218.GH27075@twins.programming.kicks-ass.net> References: <20130716202015.GX17211@twins.programming.kicks-ass.net> <1374014881.2332.21.camel@j-VirtualBox> <20130717072504.GY17211@twins.programming.kicks-ass.net> <1374048701.6000.21.camel@j-VirtualBox> <20130717093913.GP23818@dyad.programming.kicks-ass.net> <1374076741.7412.35.camel@j-VirtualBox> <20130717161815.GR23818@dyad.programming.kicks-ass.net> <51E6D9B7.1030705@redhat.com> <20130717180156.GS23818@dyad.programming.kicks-ass.net> <1374120144.1816.45.camel@j-VirtualBox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1374120144.1816.45.camel@j-VirtualBox> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1141 Lines: 25 On Wed, Jul 17, 2013 at 09:02:24PM -0700, Jason Low wrote: > I ran a few AIM7 workloads for the 8 socket HT enabled case and I needed > to set N to more than 20 in order to get the big performance gains. > > One thing that I thought of was to have N be based on how often idle > balance attempts does not pull task(s). > > For example, N can be calculated based on the number of idle balance > attempts for the CPU since the last "successful" idle balance attempt. > So if the previous 30 idle balance attempts resulted in no tasks moved, > then n = 30 / 5. So idle balance gets less time to run as the number of > unneeded idle balance attempts increases, and thus N will not be set too > high during situations where idle balancing is "successful" more often. > Any comments on this idea? It would be good to get a solid explanation for why we need such high N. But yes that might work. -- 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/