From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 5 Sep 2002 19:34:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 5 Sep 2002 19:34:20 -0400 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:52999 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Thu, 5 Sep 2002 19:34:19 -0400 To: linux-kernel@vger.kernel.org From: "H. Peter Anvin" Subject: Re: [PATCH][2.4.20-pre5] non syscall gettimeofday Date: 5 Sep 2002 16:38:35 -0700 Organization: Transmeta Corporation, Santa Clara CA Message-ID: References: <1031267553.10830.71.camel@dell_ss3.pdx.osdl.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Disclaimer: Not speaking for Transmeta in any way, shape, or form. Copyright: Copyright 2002 H. Peter Anvin - All Rights Reserved Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Followup to: <1031267553.10830.71.camel@dell_ss3.pdx.osdl.net> By author: Stephen Hemminger In newsgroup: linux.dev.kernel > > The following patch implements a shared memory interface to allow > implementing gettimeofday (and other clock measurement) using the TSC > counter on i386. On a 1.6G Xeon this reduces gettimeofday from 1.2 us > per call to .17 us per call. > This sounds like a vsyscall. Since we have discussed vsyscalls on and off without getting anywhere, I'd like to know how your implementation does it -- the #1 proposal I think was to map in a page at 0xfffff000 and have the vsyscall code there. Note that the vsyscall needs to bounce to a regular syscall if TSC time/gettimeofday aren't available. -hpa -- at work, in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt