From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422808AbXBAMCr (ORCPT ); Thu, 1 Feb 2007 07:02:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422780AbXBAMCr (ORCPT ); Thu, 1 Feb 2007 07:02:47 -0500 Received: from ns2.suse.de ([195.135.220.15]:58187 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422808AbXBAMCq (ORCPT ); Thu, 1 Feb 2007 07:02:46 -0500 From: Andi Kleen To: Ingo Molnar Subject: Re: [-mm patch] x86_64 GTOD: offer scalable vgettimeofday Date: Thu, 1 Feb 2007 13:01:51 +0100 User-Agent: KMail/1.9.5 Cc: jbohac@suse.cz, linux-kernel@vger.kernel.org, Vojtech Pavlik , arjan@infradead.org, tglx@linutronix.de, johnstul@us.ibm.com, Andrew Morton References: <20070201095952.589234000@jet.suse.cz> <20070201114644.GB26453@elte.hu> In-Reply-To: <20070201114644.GB26453@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200702011301.51834.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 01 February 2007 12:46, Ingo Molnar wrote: > > * jbohac@suse.cz wrote: > > > Inter-CPU monotonicity can not, however, be guaranteed in a vsyscall, > > so vsyscall is not used by default. [...] > > note that this is not actually the case. My patch below, ontop of -mm, > implements a fully monotonic gettimeofday as an optional vsyscall > feature. > > The 'price' paid for it is lower resolution - but it's still good for > those benchmarking TPC-C runs - and /alot/ simpler. It's also quite a > bit faster than any TSC based vgettimeofday, because it doesnt have to > do an RDTSC (or RDTSCP) instruction nor any approximation of the time. I believe that should be also a separate clock_gettime() CLOCK_ Global settings for these things are bad. Even if you run TPC-C you don't want your other programs that rely on monotonic time to break. -Andi