Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758145AbXFZO7d (ORCPT ); Tue, 26 Jun 2007 10:59:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757685AbXFZO7S (ORCPT ); Tue, 26 Jun 2007 10:59:18 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:51077 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756978AbXFZO7R (ORCPT ); Tue, 26 Jun 2007 10:59:17 -0400 Date: Tue, 26 Jun 2007 16:58:25 +0200 From: Ingo Molnar To: Mark Lord Cc: linux-kernel@vger.kernel.org, Andrew Morton , John Stultz , Thomas Gleixner Subject: Re: [patch, v2.6.22-rc6] sys_time() speedup Message-ID: <20070626145825.GA31076@elte.hu> References: <20070625200601.GA18980@elte.hu> <46805C4F.1050200@rtr.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46805C4F.1050200@rtr.ca> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -2.0 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 Content-Length: 904 Lines: 28 * Mark Lord wrote: > Ingo Molnar wrote: > >Subject: [patch] sys_time() speedup > >From: Ingo Molnar > > > >improve performance of sys_time(). sys_time() returns time in seconds, > >but it does so by calling do_gettimeofday() and then returning the > >tv_sec portion of the GTOD time. But the data structure "xtime", which > >is updated by every timer/scheduler tick, already offers HZ granularity > >time. > > How well synchronized is xtime with real-time ? it's updated by every jiffy. > Programs invoking sys_time() do expect it to be as accurate as > gettimeofday(), even if only at 1-second boundaries. yes. Ingo - 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/