From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751909Ab2GTSeG (ORCPT ); Fri, 20 Jul 2012 14:34:06 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:53665 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751380Ab2GTSeF (ORCPT ); Fri, 20 Jul 2012 14:34:05 -0400 Date: Fri, 20 Jul 2012 11:34:00 -0700 From: Tejun Heo To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, tglx@linutronix.de, linux-pm@vger.kernel.org, "Rafael J. Wysocki" Subject: Re: [PATCHSET] workqueue: reimplement CPU hotplug to keep idle workers Message-ID: <20120720183400.GL32763@google.com> References: <1342545149-3515-1-git-send-email-tj@kernel.org> <1342799311.2583.7.camel@twins> <20120720170255.GE32763@google.com> <1342804877.2583.42.camel@twins> <20120720175041.GI32763@google.com> <1342808550.2583.48.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1342808550.2583.48.camel@twins> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Fri, Jul 20, 2012 at 08:22:30PM +0200, Peter Zijlstra wrote: > I really think people who use hotplug at high frequencies are on drugs > and doing it wrong. I don't know. It does make some sense. It's not like we have any other mechanism to keep some processors completely quiesient, which could make a noticeable difference from powersaving POV compared to mostly idle. Rafael, can you please chime in and explain how / where / how freqeuntly / etc CPU hotplug is used for powersaving? Thanks. -- tejun