Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932583AbVLMVQe (ORCPT ); Tue, 13 Dec 2005 16:16:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932506AbVLMVQe (ORCPT ); Tue, 13 Dec 2005 16:16:34 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:23006 "EHLO e31.co.us.ibm.com") by vger.kernel.org with ESMTP id S932583AbVLMVQc (ORCPT ); Tue, 13 Dec 2005 16:16:32 -0500 Subject: Re: [Lse-tech] [RFC][Patch 1/5] nanosecond timestamps and diffs From: john stultz To: Jay Lan Cc: Shailabh Nagar , Christoph Lameter , linux-kernel , elsa-devel , lse-tech@lists.sourceforge.net, ckrm-tech , Guillaume Thouvenin , Jay Lan , Jens Axboe In-Reply-To: <439F1455.7080402@engr.sgi.com> References: <43975D45.3080801@watson.ibm.com> <43975E6D.9000301@watson.ibm.com> <439DD01A.2060803@watson.ibm.com> <1134416962.14627.7.camel@cog.beaverton.ibm.com> <439F1455.7080402@engr.sgi.com> Content-Type: text/plain Date: Tue, 13 Dec 2005 13:16:26 -0800 Message-Id: <1134508587.12313.10.camel@leatherman> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1381 Lines: 38 On Tue, 2005-12-13 at 10:35 -0800, Jay Lan wrote: > john stultz wrote: > > On Mon, 2005-12-12 at 19:31 +0000, Shailabh Nagar wrote: > >>Christoph Lameter wrote: > >>>On Wed, 7 Dec 2005, Shailabh Nagar wrote: > >>>>+void getnstimestamp(struct timespec *ts) > >>> > >>>There is already getnstimeofday in the kernel. > >> > >>Yes, and that function is being used within the getnstimestamp() being proposed. > >>However, John Stultz had advised that getnstimeofday could get affected by calls to > >>settimeofday and had recommended adjusting the getnstimeofday value with wall_to_monotonic. > >> > >>John, could you elaborate ? > > > > I think you pretty well have it covered. > > > > getnstimeofday + wall_to_monotonic should be higher-res and more > > reliable (then TSC based sched_clock(), for example) for getting a > > timestamp. > > How is this proposed function different from > do_posix_clock_monotonic_gettime()? > It calls getnstimeofday(), it also adjusts with wall_to_monotinic. > > It seems to me we just need to EXPORT_SYMBOL_GPL the > do_posix_clock_monotonic_gettime()? Indeed, this would be the same. thanks -john - 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/