Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756631AbZJ0SUH (ORCPT ); Tue, 27 Oct 2009 14:20:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756579AbZJ0SUH (ORCPT ); Tue, 27 Oct 2009 14:20:07 -0400 Received: from claw.goop.org ([74.207.240.146]:38865 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756575AbZJ0SUG (ORCPT ); Tue, 27 Oct 2009 14:20:06 -0400 Message-ID: <4AE739DA.20601@goop.org> Date: Tue, 27 Oct 2009 11:20:10 -0700 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20091014 Fedora/3.0-2.8.b4.fc11 Lightning/1.0pre Thunderbird/3.0b4 MIME-Version: 1.0 To: Dan Magenheimer CC: Avi Kivity , Jeremy Fitzhardinge , kurt.hackel@oracle.com, the arch/x86 maintainers , Linux Kernel Mailing List , Glauber de Oliveira Costa , Xen-devel , Keir Fraser , zach.brown@oracle.com, chris.mason@oracle.com, Ingo Molnar Subject: Re: [Xen-devel] Re: [PATCH 3/5] x86/pvclock: add vsyscall implementation References: <4f079cd6-0872-4cb5-832b-ee6a46841192@default> In-Reply-To: <4f079cd6-0872-4cb5-832b-ee6a46841192@default> X-Enigmail-Version: 0.97a Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 821 Lines: 19 On 10/27/09 10:29, Dan Magenheimer wrote: > Is there any way for an application to conclusively determine > programmatically if the "fast vsyscall" pvclock is functional > vs the much much slower gettimeofday/clock_gettime equivalents? > > If not, might it be possible to implement some (sysfs?) > way to determine this, that would also be backwards compatible > to existing OS's that don't have pvclock+vsyscall supported? > It would probably be simplest and most portable for the app to just measure the performance of gettimeofday and see if it meets its needs. J -- 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/