From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Cochran Subject: Re: [PATCH v4 1/4] Produce system time from correlated clocksource Date: Tue, 20 Oct 2015 10:54:08 +0200 Message-ID: <20151020085408.GA2542@netboy> References: <1444675522-4198-1-git-send-email-christopher.s.hall@intel.com> <1444675522-4198-2-git-send-email-christopher.s.hall@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christopher Hall , Thomas Gleixner , Jeff Kirsher , "H. Peter Anvin" , Ingo Molnar , Peter Zijlstra , "x86@kernel.org" , intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, lkml , kevin.b.stanton@intel.com To: John Stultz Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, Oct 19, 2015 at 05:36:56PM -0700, John Stultz wrote: > If we're only tracking 4ms of history, how does this solution > measurably improve the error over using the timestamps to generate > MONOTONIC_RAW clock deltas (which doesn't require keeping any history) > and using getnstime_raw_and_real to take an anchor point to calculate > the delta from? Why is adding complexity necessary? This idea is variant of what I suggested in another reply in this thread. To my understanding, there is no need at all to keep a history arbitrarily 4 ms long. Instead, the DSP driver (or whoever else may need such a thing) can simply sample the system time at the rate needed for that particular application. Thanks, Richard