Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262321AbVEMJTh (ORCPT ); Fri, 13 May 2005 05:19:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262318AbVEMJTb (ORCPT ); Fri, 13 May 2005 05:19:31 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:26280 "EHLO e5.ny.us.ibm.com") by vger.kernel.org with ESMTP id S262316AbVEMJTZ (ORCPT ); Fri, 13 May 2005 05:19:25 -0400 Date: Fri, 13 May 2005 14:49:24 +0530 From: Srivatsa Vaddagiri To: Nick Piggin Cc: Ingo Molnar , Martin Schwidefsky , george@mvista.com, jdike@addtoit.com, Jesse Barnes , linux-kernel@vger.kernel.org, Lee Revell , Tony Lindgren Subject: Re: [RFC] (How to) Let idle CPUs sleep Message-ID: <20050513091924.GG23705@in.ibm.com> Reply-To: vatsa@in.ibm.com References: <20050512171251.GA21656@in.ibm.com> <20050513062330.GD23705@in.ibm.com> <42845456.3080908@yahoo.com.au> <20050513080424.GA31206@elte.hu> <428464D5.10702@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <428464D5.10702@yahoo.com.au> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1270 Lines: 33 On Fri, May 13, 2005 at 08:29:17AM +0000, Nick Piggin wrote: > And don't forget that the watchdog approach can just as easily deep > sleep a CPU only to immediately wake it up again if it detects an > imbalance. I think we should increase the threshold beyond which the idle CPU is woken up (more than the imbalance_pct that exists already). This should justify waking up the CPU. > And the CPU usage / wakeup cost arguments cut both ways. The busy > CPUs have to do extra work in the watchdog case. Maybe with a really smart watchdog solution, we can cut down this overhead. I did think of other schemes - a dedicated CPU per node acting as watchdog for that node and per-node wacthdog kernel threads? - to name a few. What I had proposed was the best I thought. But maybe we can look at improving it to see if the overhead concern you have can be reduced - meeting the interests of both the worlds :) -- 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/