Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755231Ab2FFIk1 (ORCPT ); Wed, 6 Jun 2012 04:40:27 -0400 Received: from casper.infradead.org ([85.118.1.10]:59417 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755023Ab2FFIkX convert rfc822-to-8bit (ORCPT ); Wed, 6 Jun 2012 04:40:23 -0400 Message-ID: <1338972010.2749.74.camel@twins> Subject: RE: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi From: Peter Zijlstra To: Thomas Gleixner Cc: "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" Date: Wed, 06 Jun 2012 10:40:10 +0200 In-Reply-To: References: <1338833876-29721-1-git-send-email-fenghua.yu@intel.com> <1338842001.28282.135.camel@twins> <87zk8iioam.fsf@rustcorp.com.au> <1338881971.28282.150.camel@twins> <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> <1338931856.2749.57.camel@twins> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1059 Lines: 26 On Wed, 2012-06-06 at 00:09 +0200, Thomas Gleixner wrote: > We have no mechanism to exclude those cpus from general > "oh you should do X and Y" tasks which are not really necessary at > all. Its that latter part which makes this nearly impossible. How do you tell its not really necessary? Look at the patches Gilad did, there is very little common code between each of those cases. We cannot just not flush objects because the cpu is supposed to be isolated. If it has buffer they need flushing. Not doing so would lead to memory leaks at best and crashes at worst. Some people want isolation to never use system calls, those are the easy case. But the isolation case where the apps do use plenty system calls but just don't want to deal with the perturbations of other workloads are much harder to sort. -- 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/