From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422832AbXBAMRu (ORCPT ); Thu, 1 Feb 2007 07:17:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422833AbXBAMRu (ORCPT ); Thu, 1 Feb 2007 07:17:50 -0500 Received: from ns1.suse.de ([195.135.220.2]:34145 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422832AbXBAMRt (ORCPT ); Thu, 1 Feb 2007 07:17:49 -0500 From: Andi Kleen To: Ingo Molnar Subject: Re: [-mm patch] x86_64 GTOD: offer scalable vgettimeofday II Date: Thu, 1 Feb 2007 13:17:45 +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: <200702011317.45876.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. BTW another comment: I was told that at least one of the big databases wants ms resolution here. So to make your scheme work would require a HZ=1024 regular interrupt. But that would also make everything slower again due to CPU overhead as it was learned in the 2.4->2.6 HZ transition. So it might not actually be worth it. -Andi