Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262257AbVEMGXi (ORCPT ); Fri, 13 May 2005 02:23:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261400AbVEMGXi (ORCPT ); Fri, 13 May 2005 02:23:38 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:9350 "EHLO e3.ny.us.ibm.com") by vger.kernel.org with ESMTP id S262257AbVEMGXa (ORCPT ); Fri, 13 May 2005 02:23:30 -0400 Date: Fri, 13 May 2005 11:53:30 +0530 From: Srivatsa Vaddagiri To: Martin Schwidefsky Cc: george@mvista.com, jdike@addtoit.com, Jesse Barnes , linux-kernel@vger.kernel.org, Ingo Molnar , Nick Piggin , Lee Revell , Tony Lindgren Subject: Re: [RFC] (How to) Let idle CPUs sleep Message-ID: <20050513062330.GD23705@in.ibm.com> Reply-To: vatsa@in.ibm.com References: <20050512171251.GA21656@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1472 Lines: 36 On Thu, May 12, 2005 at 08:08:26PM +0200, Martin Schwidefsky wrote: > I would prefer a solution where the busy CPU wakes up an idle CPU if the > imbalance is too large. Any scheme that requires an idle CPU to poll at > some intervals will have one of two problem: either the poll intervall > is large then the imbalance will stay around for a long time, or the > poll intervall is small then this will behave badly in a heavily > virtualized environment with many images. I guess all the discussions we are having boils down to this: what is the max time one can afford to have an imbalanced system because of sleeping idle CPU not participating in load balance? 10ms, 100ms, 1 sec or more? Maybe the answer depends on how much imbalance it is that we are talking of here. A high order of imbalance would mean that the sleeping idle CPUs have to be woken up quickly, while a low order imbalance could mean that we can let it sleep longer. >From all the discussions we have been having, I think a watchdog implementation makes more sense. Nick/Ingo, what do you think should be our final decision on this? -- Thanks and Regards, Srivatsa Vaddagiri, Linux Technology Center, IBM Software Labs, Bangalore, INDIA - 560017 - 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/