From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756481Ab1BXUQ1 (ORCPT ); Thu, 24 Feb 2011 15:16:27 -0500 Received: from www.tglx.de ([62.245.132.106]:50782 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754646Ab1BXUQZ (ORCPT ); Thu, 24 Feb 2011 15:16:25 -0500 Date: Thu, 24 Feb 2011 21:16:01 +0100 (CET) From: Thomas Gleixner To: Alan Cox cc: Peter Zijlstra , Vincent Guittot , linux-kernel@vger.kernel.org, linux-hotplug@vger.kernel.org, Frederic Weisbecker , Steven Rostedt , amit.kucheria@linaro.org, Rusty Russell , Ingo Molnar Subject: Re: [PATCH V5 2/2] tracing, perf : add cpu hotplug trace events In-Reply-To: <20110224201124.138311ba@lxorguk.ukuu.org.uk> Message-ID: References: <1298573197.2428.457.camel@twins> <20110224201124.138311ba@lxorguk.ukuu.org.uk> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 24 Feb 2011, Alan Cox wrote: > > Anybody who is interested in the latency of cpu hotplug is deluding > > himself, also cpu hotplug is _NOT_ a power management feature, so the > > rest of your justification just disappeared as well. > > Actually CPU hotplug is a power management feature on some devices where > you need to shutdown one of the cores to enter low power modes. Right. > Remember we use it as part of the suspend paths and various processors > nowdays drop into a suspend to RAM type state on CPU idling. The suspend path is using it, but the cpu idle one is hardly using the hotplug muck. Thanks, tglx