Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932618AbVLMXLx (ORCPT ); Tue, 13 Dec 2005 18:11:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932620AbVLMXLw (ORCPT ); Tue, 13 Dec 2005 18:11:52 -0500 Received: from e3.ny.us.ibm.com ([32.97.182.143]:32680 "EHLO e3.ny.us.ibm.com") by vger.kernel.org with ESMTP id S932618AbVLMXLv (ORCPT ); Tue, 13 Dec 2005 18:11:51 -0500 Subject: Re: [ckrm-tech] Re: [Lse-tech] [RFC][Patch 1/5] nanosecond timestamps and diffs From: Matt Helsley To: Jay Lan Cc: john stultz , 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 15:05:59 -0800 Message-Id: <1134515159.6617.196.camel@stark> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1931 Lines: 62 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()? > > Thanks, > - jay Ah, yes. I should've searched for gettime rather than gettimeofday when I was looking for a suitable function. Two minor differences exist: 1) getnstimestamp does not fetch an unused copy of jiffies_64 2) getnstimestamp uses and advertises an explicit maximum resolution I don't think either of these really matter so I'll post a series of patches: 1) EXPORTing (_SYMBOL_GPL) do_posix_clock_monotonic_gettime() 2) using do_posix_clock_monotonic_gettime() as a timestamp 3) removing getnstimestamp() Thanks, -Matt Helsley - 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/