Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750759AbVK3BWx (ORCPT ); Tue, 29 Nov 2005 20:22:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750762AbVK3BWx (ORCPT ); Tue, 29 Nov 2005 20:22:53 -0500 Received: from mustang.oldcity.dca.net ([216.158.38.3]:24770 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S1750759AbVK3BWx (ORCPT ); Tue, 29 Nov 2005 20:22:53 -0500 Subject: Re: [RFC][PATCH] Runtime switching of the idle function [take 2] From: Lee Revell To: Andi Kleen Cc: "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, Vojtech Pavlik In-Reply-To: <20051130010646.GD19515@wotan.suse.de> References: <20051129195336.GP19515@wotan.suse.de> <1133296540.4627.7.camel@mindpipe> <20051129205108.GQ19515@wotan.suse.de> <1133308505.4627.31.camel@mindpipe> <20051130010646.GD19515@wotan.suse.de> Content-Type: text/plain Date: Tue, 29 Nov 2005 20:22:50 -0500 Message-Id: <1133313771.4627.39.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.4.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1216 Lines: 38 On Wed, 2005-11-30 at 02:06 +0100, Andi Kleen wrote: > > But on my system gettimeofday uses the TSC and it's still ~35x slower > > than RDTSC: > > > > rlrevell@mindpipe:~$ ./timetest > > rdtsc: 10000 calls in 1079 usecs > > gettimeofday: 10000 calls in 36628 usecs > > First if you run this on an Athlon 64 the measurement is likely > wrong because RDTSC can be speculated around. To get accurate > data you need to add synchronizing instructions. > OK. Just for reference here's what people on the JACK list reported: 2.6.14-rt13, PREEMPT_RT, Athlon X2 4400+ (dual core) rdtsc: 10000 calls in 68 usecs gettimeofday: 10000 calls in 5170 usecs P4@3.3Ghz/HT (OpenSUSE 10.0 2.6.13-15-smp): rdtsc: 10000 calls in 253 usecs gettimeofday: 10000 calls in 26547 usecs > Then you're likely running 32bit. It doesn't use vsyscall gettimeofday > yet, which makes it slower. 64bit would. Yes, I am. So it sounds like vsyscall gettimeofday for i386 is in the works? Lee - 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/