From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965548AbXCLLEl (ORCPT ); Mon, 12 Mar 2007 07:04:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965547AbXCLLEl (ORCPT ); Mon, 12 Mar 2007 07:04:41 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:36628 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965538AbXCLLEj (ORCPT ); Mon, 12 Mar 2007 07:04:39 -0400 Date: Mon, 12 Mar 2007 12:04:17 +0100 From: Ingo Molnar To: Andi Kleen Cc: Thomas Gleixner , Roland McGrath , akpm@linux-foundation.org, mm-commits@vger.kernel.org, npiggin@suse.de, drepper@redhat.com, oleg@tv-sign.ru, sebastien.dugue@bull.net, linux-kernel@vger.kernel.org Subject: Re: [patch] change futex_wait() to hrtimers Message-ID: <20070312110417.GA12308@elte.hu> References: <200703110814.l2B8EaI1007615@shell0.pdx.osdl.net> <20070312011259.3834A1801C4@magilla.sf.frob.com> <20070312091006.GF21024@elte.hu> <1173697220.13341.84.camel@localhost.localdomain> <20070312105826.GB11864@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070312105826.GB11864@one.firstfloor.org> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Andi Kleen wrote: > On Mon, Mar 12, 2007 at 12:00:20PM +0100, Thomas Gleixner wrote: > > On Mon, 2007-03-12 at 12:27 +0100, Andi Kleen wrote: > > > Ingo Molnar writes: > > > > > > > > the only correct approach is the use of hrtimers, and a patch exists for > > > > that - see below. This has been included in -rt for quite some time. > > > > > > But isn't that bad for power management? You'll likely get more > > > idle wakeups, won't you? > > > > Why so ? It comes more precise, but only once. > > When it's clustered around the jiffies interval then wakeups from > multiple processes will be somewhat batched. With a precise wakeup > you'll get wakeups all over the jiffies period, won't you? if HIGH_RES_TIMERS is disabled then that is what happens. But frankly, most futex waits are without timeouts - if an application cares about micro-effects like that then you are much better off not using a per-futex timeout anyway. Ingo