Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752699Ab2FEP1K (ORCPT ); Tue, 5 Jun 2012 11:27:10 -0400 Received: from mga01.intel.com ([192.55.52.88]:30435 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751488Ab2FEP1H (ORCPT ); Tue, 5 Jun 2012 11:27:07 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="175065068" Message-ID: <4FCE254A.6050504@linux.intel.com> Date: Tue, 05 Jun 2012 08:27:06 -0700 From: Arjan van de Ven User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Alan Stern CC: Rusty Russell , Peter Zijlstra , Thomas Gleixner , Fenghua Yu , Ingo Molnar , H Peter Anvin , Suresh B Siddha , Tony Luck , Asit K Mallick , linux-kernel , x86 , linux-pm , "Srivatsa S. Bhat" Subject: Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi References: In-Reply-To: X-Enigmail-Version: 1.4.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1102 Lines: 27 On 6/5/2012 7:17 AM, Alan Stern wrote: > On Mon, 4 Jun 2012, Arjan van de Ven wrote: > >>> I disagree. Deactivating a cpu for power saving is halfway to hotplug >>> anyway. I'd rather unify the two cases, where we can specify how dead a >>> CPU should be, than have individual archs and boards do random hacks. >> >> well on PC's there really is no difference at least; >> idle equals "all power removed" already there. > > This doesn't sound right at all. Len Brown has often told us that on > Intel chips, power can't be removed from a package until _all_ the > cores in the package are idle. but "cpu hotplug" does not change that.. in fact, cpu hotplug is implemented as a C state... and to be specific; power will get removed from the cores one at a time. you just cannot remove the power from the memory controller until the last one is off. -- 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/