Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932400AbVK2UvO (ORCPT ); Tue, 29 Nov 2005 15:51:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932401AbVK2UvN (ORCPT ); Tue, 29 Nov 2005 15:51:13 -0500 Received: from cantor.suse.de ([195.135.220.2]:55936 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S932400AbVK2UvN (ORCPT ); Tue, 29 Nov 2005 15:51:13 -0500 Date: Tue, 29 Nov 2005 21:51:09 +0100 From: Andi Kleen To: Lee Revell Cc: Andi Kleen , "Brown, Len" , Nick Piggin , Ingo Molnar , Steven Rostedt , Andrew Morton , acpi-devel@lists.sourceforge.net, nando@ccrma.Stanford.EDU, linux-kernel@vger.kernel.org, paulmck@us.ibm.com, kr@cybsft.com, tglx@linutronix.de, pluto@agmk.net, john.cooper@timesys.com, bene@linutronix.de, dwalker@mvista.com, trini@kernel.crashing.org, george@mvista.com Subject: Re: [RFC][PATCH] Runtime switching of the idle function [take 2] Message-ID: <20051129205108.GQ19515@wotan.suse.de> References: <20051129195336.GP19515@wotan.suse.de> <1133296540.4627.7.camel@mindpipe> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1133296540.4627.7.camel@mindpipe> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1131 Lines: 27 On Tue, Nov 29, 2005 at 03:35:39PM -0500, Lee Revell wrote: > On Tue, 2005-11-29 at 20:53 +0100, Andi Kleen wrote: > > We're mostly addressing it - there are problems left, but > > overall it's looking good. The remaining problem is > > an education issue of users to not use RDTSC directly, > > but use gettimeofday/clock_gettime > > No the issue is to make gettimeofday fast enough that the people who > currently have to use the TSC can use it. Right now it's 1500-3000 nsec > or so, Vojtech mentioned that he has a patch that could reduce that to It's only that slow if the hardware can't do better. And the kernel makes it only slow when using RDTSC directly is unsafe - so if you use it directly thinking the kernel cheats you for your cycles you're just shoting yourself in the own foot. > 150-300 nsec. If you have capable hardware it can already do much better. -Andi - 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/