Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751469AbVIVKca (ORCPT ); Thu, 22 Sep 2005 06:32:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751470AbVIVKcJ (ORCPT ); Thu, 22 Sep 2005 06:32:09 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:60585 "EHLO atrey.karlin.mff.cuni.cz") by vger.kernel.org with ESMTP id S1751468AbVIVKcF (ORCPT ); Thu, 22 Sep 2005 06:32:05 -0400 Date: Wed, 21 Sep 2005 21:24:44 +0200 From: Pavel Machek To: Christoph Lameter Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, mingo@elte.hu, akpm@osdl.org, george@mvista.com, johnstul@us.ibm.com, paulmck@us.ibm.com Subject: Re: [ANNOUNCE] ktimers subsystem Message-ID: <20050921192444.GD467@openzaurus.ucw.cz> References: <20050919184834.1.patchmail@tglx.tec.linutronix.de> <1127168232.24044.265.camel@tglx.tec.linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.3.27i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1380 Lines: 32 Hi! > > Also the basic prerequisite for for high resolution timers is a fast and > > simple access to clock_monotonic rather than to a backward corrected > > clock_realtime representation. > > Yup that may be a reason to tolerate the add for realtime. > > > We should rather ask glibc people why gettimeofday() / clock_getttime() > > is called inside the library code all over the place for non obvious > > reasons. > > You can ask lots of application vendors the same question because its all > over lots of user space code. The fact is that gettimeofday() / > clock_gettime() efficiency is very critical to the performance of many > applications on Linux. That is why the addtion of one add instruction may > better be carefully considered. Many platforms can execute gettimeofday > without having to enter the kernel. Eh? One addition is going to be lost in noise compared to syscall overhead. (For vsyscall, you may be closer to truth, but I doubt it. You could still gain more than one addition by using some strange calling convention). -- 64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms - 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/