From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261191AbVFUAFi (ORCPT ); Mon, 20 Jun 2005 20:05:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261500AbVFUADl (ORCPT ); Mon, 20 Jun 2005 20:03:41 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:36803 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S261191AbVFTXl3 (ORCPT ); Mon, 20 Jun 2005 19:41:29 -0400 Subject: Re: [PATCH 1/6] new timeofday core subsystem for -mm (v.B3) From: Lee Revell To: john stultz Cc: Roman Zippel , lkml , Andrew Morton , George Anzinger , Ulrich Windl In-Reply-To: <1119304422.9947.90.camel@cog.beaverton.ibm.com> References: <1119063400.9663.2.camel@cog.beaverton.ibm.com> <1119287354.9947.22.camel@cog.beaverton.ibm.com> <1119291034.16180.9.camel@mindpipe> <1119304422.9947.90.camel@cog.beaverton.ibm.com> Content-Type: text/plain Date: Mon, 20 Jun 2005 19:44:56 -0400 Message-Id: <1119311096.17701.3.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2005-06-20 at 14:53 -0700, john stultz wrote: > Yea, honestly I doubt gettimefoday performance will ever be as good as > rdtsc. I mean, that's a single instruction vs syscall overhead + > hardware clock reading + frequency conversion + ntp adjustment. Its > just not a fair comparison. Of course not, the patch would have to be magic for that to happen. But some user space apps are now *required* to use rdtsc for timing due to the massive performance difference. If we only took a 5x or 10x performance hit vs rdtsc, rather than the current 50x, it might be enough that user space apps won't have to do this. Lee