From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764217AbXGPL6B (ORCPT ); Mon, 16 Jul 2007 07:58:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757180AbXGPL5x (ORCPT ); Mon, 16 Jul 2007 07:57:53 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:34346 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755621AbXGPL5w (ORCPT ); Mon, 16 Jul 2007 07:57:52 -0400 Date: Mon, 16 Jul 2007 13:57:44 +0200 From: Ingo Molnar To: Roman Zippel Cc: Jonathan Corbet , linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH/RFC] msleep() with hrtimers Message-ID: <20070716115744.GA14131@elte.hu> References: <19044.1184539364@lwn.net> <20070716114734.GA12010@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -1.0 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 * Roman Zippel wrote: > > > One possible problem here is that setting up that timer can be > > > considerably more expensive, for a relative timer you have to read > > > the current time, which can be quite expensive (e.g. your machine > > > now uses the PIT timer, because TSC was deemed unstable). > > > > i dont think there's any significant overhead. The OLPC folks are > > pretty sensitive to performance, so if there was any genuine > > measurable overhead due to this, i'd expect them to report it. And > > even if there _was_ overhead, it would be well worth its price, the > > legacies of HZ are clearly biting the OLPC project here. The sooner > > we get rid of HZ dependencies and HZ artifacts, the better. > > How is a sleep function relevant to performace? i'm not sure how your question relates/connects to what i wrote above, could you please re-phrase your question into a bit more verbose form so that i can answer it? Thanks, Ingo