Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757477Ab2FDUdm (ORCPT ); Mon, 4 Jun 2012 16:33:42 -0400 Received: from casper.infradead.org ([85.118.1.10]:34699 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752760Ab2FDUdk convert rfc822-to-8bit (ORCPT ); Mon, 4 Jun 2012 16:33:40 -0400 Message-ID: <1338842001.28282.135.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: Fenghua Yu , Ingo Molnar , H Peter Anvin , Suresh B Siddha , Tony Luck , Asit K Mallick , Arjan Dan De Ven , linux-kernel , x86 , linux-pm , "Srivatsa S. Bhat" , Rusty Russell Date: Mon, 04 Jun 2012 22:33:21 +0200 In-Reply-To: References: <1338833876-29721-1-git-send-email-fenghua.yu@intel.com> 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: 1329 Lines: 28 On Mon, 2012-06-04 at 22:11 +0200, Thomas Gleixner wrote: > I understand what you are trying to do, though I completely disagree > with the solution. > > The main problem of the current hotplug code is that it is an all or > nothing approach. You have to tear down the whole thing completely > instead of just taking it out of the usable set of cpus. > > I'm working on a proper state machine driven online/offline sequence, > where you can put the cpu into an intermediate state which avoids > bringing it down completely. This is enough to get the full > powersaving benefits w/o having to go through all the synchronization > states of a full online/offline. That will shorten the onlining time > of an previously offlined cpu to almost nothing. > > I really want to avoid adding more bandaids to the hotplug code before > we have sorted out the existing horror. Its far worse.. you shouldn't _ever_ care about hotplug latency unless you've got absolutely braindead hardware. We all now ARM has been particularly creative here, but is Intel now trying to trump ARM at stupid? -- 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/