Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute cycle count

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute cycle count
Date	2016-11-18 16:00 +0100
Message-ID	<sESNX-8ud-3@gated-at.bofh.it> (permalink)
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On Fri, Nov 18, 2016 at 09:24:52AM -0500, Chris Metcalf wrote:
> I would think you would also unnecessarily accumulate small errors.

True..

> The x86 sched_clock() seems to purely scale the current TSC value,
> so what tile is doing is consistent with that, at least.

Right, this comes apart the moment TSC goes faster than 1GHz though.
Which might actually be the case, because then the mult-and-shift
reduces resolution and we'd wrap before the 64bit are done.

That would be something I ought to look at some time..

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[PATCH v2] tile: avoid using clocksource_cyc2ns with absolute cycle count Chris Metcalf <cmetcalf@mellanox.com> - 2016-11-16 20:40 +0100
  Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute  cycle count John Stultz <john.stultz@linaro.org> - 2016-11-16 21:00 +0100
    Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute  cycle count John Stultz <john.stultz@linaro.org> - 2016-11-16 21:30 +0100
      Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute  cycle count John Stultz <john.stultz@linaro.org> - 2016-11-16 21:40 +0100
    Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute  cycle count Peter Zijlstra <peterz@infradead.org> - 2016-11-17 11:00 +0100
      Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute  cycle count Peter Zijlstra <peterz@infradead.org> - 2016-11-18 11:40 +0100
        Re: [PATCH v2] tile: avoid using clocksource_cyc2ns with absolute  cycle count Peter Zijlstra <peterz@infradead.org> - 2016-11-18 16:00 +0100

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