From: Thomas Gleixner <tglx@linutronix.de>
To: Richard Cochran <richardcochran@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>,
Christopher Hall <christopher.s.hall@intel.com>,
Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
"x86@kernel.org" <x86@kernel.org>,
intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
lkml <linux-kernel@vger.kernel.org>,
kevin.b.stanton@intel.com
Subject: Re: [PATCH v4 1/4] Produce system time from correlated clocksource
Date: Tue, 20 Oct 2015 12:48:03 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.11.1510201246250.3982@nanos> (raw)
In-Reply-To: <20151020085408.GA2542@netboy>
On Tue, 20 Oct 2015, Richard Cochran wrote:
> 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.
That's complete nonsense. The whole point is to have a proper
correlation from ART/audio timestamps to system time. Sampling system
time does not help in any way,
Thanks,
tglx
next prev parent reply other threads:[~2015-10-20 10:48 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-12 18:45 [PATCH v4 0/4] Patchset enabling hardware based cross-timestamps for next gen Intel platforms Christopher S. Hall
2015-10-12 18:45 ` [PATCH v4 1/4] Produce system time from correlated clocksource Christopher S. Hall
2015-10-13 4:58 ` Richard Cochran
2015-10-13 7:51 ` Thomas Gleixner
2015-10-13 8:31 ` Richard Cochran
2015-10-13 19:15 ` Thomas Gleixner
2015-10-13 21:12 ` Richard Cochran
2015-10-14 7:21 ` Thomas Gleixner
2015-10-14 9:29 ` Richard Cochran
2015-10-14 14:22 ` Thomas Gleixner
2015-10-14 16:18 ` Richard Cochran
2015-10-15 2:34 ` Christopher Hall
2015-10-15 5:41 ` Richard Cochran
2015-10-15 8:13 ` Thomas Gleixner
2015-10-13 5:26 ` Richard Cochran
2015-10-13 13:50 ` Richard Cochran
2015-10-13 19:42 ` Thomas Gleixner
2015-10-15 1:57 ` Christopher Hall
2015-10-15 5:57 ` Richard Cochran
2015-10-15 8:15 ` Thomas Gleixner
2015-10-20 0:18 ` Christopher Hall
2015-10-20 0:36 ` John Stultz
2015-10-20 8:54 ` Richard Cochran
2015-10-20 10:48 ` Thomas Gleixner [this message]
2015-10-20 11:51 ` Richard Cochran
2015-10-20 14:55 ` Richard Cochran
2015-10-20 19:11 ` Thomas Gleixner
2015-10-20 19:36 ` Richard Cochran
2015-10-20 20:16 ` John Stultz
2015-10-21 7:44 ` Thomas Gleixner
2015-11-03 19:18 ` Stanton, Kevin B
2015-11-09 21:17 ` John Stultz
2015-10-12 18:45 ` [PATCH v4 2/4] Always running timer " Christopher S. Hall
2015-10-13 2:03 ` kbuild test robot
2015-11-18 23:53 ` Jacob Pan
2015-10-12 18:45 ` [PATCH v4 3/4] Add PTP_SYS_OFFSET_PRECISE for driver crosstimestamping Christopher S. Hall
2015-10-13 13:59 ` Richard Cochran
2015-10-15 2:47 ` Christopher Hall
2015-11-07 2:15 ` Christopher Hall
2015-10-12 18:45 ` [PATCH v4 4/4] Adds hardware supported cross timestamp Christopher S. Hall
2015-10-13 2:10 ` kbuild test robot
2015-10-13 2:11 ` kbuild test robot
2015-10-13 2:31 ` David Miller
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