Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752832Ab2FEWBf (ORCPT ); Tue, 5 Jun 2012 18:01:35 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:47467 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751951Ab2FEWBd (ORCPT ); Tue, 5 Jun 2012 18:01:33 -0400 Date: Tue, 5 Jun 2012 15:00:59 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Thomas Gleixner , "Luck, Tony" , "Yu, Fenghua" , Rusty Russell , Ingo Molnar , H Peter Anvin , "Siddha, Suresh B" , "Mallick, Asit K" , Arjan Dan De Ven , linux-kernel , x86 , linux-pm , "Srivatsa S. Bhat" Subject: Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi Message-ID: <20120605220059.GV2388@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <3E5A0FA7E9CA944F9D5414FEC6C7122007727023@ORSMSX105.amr.corp.intel.com> <1338912565.2749.9.camel@twins> <3E5A0FA7E9CA944F9D5414FEC6C7122007728081@ORSMSX105.amr.corp.intel.com> <1338913190.2749.10.camel@twins> <3908561D78D1C84285E8C5FCA982C28F19300965@ORSMSX104.amr.corp.intel.com> <1338918625.2749.29.camel@twins> <1338925756.2749.36.camel@twins> <20120605212947.GA8686@linux.vnet.ibm.com> <1338932241.2749.62.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1338932241.2749.62.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12060522-5518-0000-0000-000004F18E2E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1754 Lines: 40 On Tue, Jun 05, 2012 at 11:37:21PM +0200, Peter Zijlstra wrote: > On Tue, 2012-06-05 at 14:29 -0700, Paul E. McKenney wrote: > > OK, I'll bite... Why not just use CPU hotplug to expel the timers? > > Currently? Can you say: 'kstopmachine'? So if CPU hotplug (or whatever you want to call it) stops using kstopmachine, you are OK with it? > But its also a question of interface and naming. Do you want to have to > iterate all cpus in your isolated set, do you want to bring them down > far enough to physically unplug. Ideally no to both. For many use cases, it is indeed not necessary to get to a point where the CPUs could be physically removed from the system. But CPU-failure use cases would need the CPU to be fully deactivated. And many of the hardware guys tell me that the CPU-failure case will be getting more common, though I sure hope that they are wrong. > If you don't bring them down far enough to unplug, should you still be > calling it hotplug? I am not too worried about what it is called. Though "banish to monastery" would probably be going too far in the other direction. > Ideally I think there'd be a file in your cpuset which if opened and > written to will flush all pending bits (timers, workqueues, the lot) and > return when this is done (and maybe provide O_ASYNC writes to not wait > for completion). The mobile guys probably are not too worried about bulk operations yet because they don't have that many CPUs, but it might be useful elsewhere. Thanx, Paul -- 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/