linux-kernel - Re: [PATCH v3 1/4] Add correlated clocksource deriving system time from an auxiliary clocksource

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Message-ID: <20150904154133.GI18489@twins.programming.kicks-ass.net>
Date:	Fri, 4 Sep 2015 17:41:33 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"Hall, Christopher S" <christopher.s.hall@...el.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
Subject: Re: [PATCH v3 1/4] Add correlated clocksource deriving system time
 from an auxiliary clocksource

On Fri, Sep 04, 2015 at 05:17:43PM +0200, Richard Cochran wrote:
> On Fri, Sep 04, 2015 at 05:10:21PM +0200, Peter Zijlstra wrote:
> > I think what they're getting at is asking if there's a rate limit to
> > time adjustments, without that, saving the last n transition points will
> > still not cover any given length of history.
> 
> As if the ntp code isn't complex enough already - now we're adding
> sample histories and adjustment rating limiting?
> 
> And all for some unknown DSP in a mythical sound card??

Hehe, I'm just a 'translator' here. But going by you answer I'm taking
it there isn't in fact a rate-limit to adjustments. Which, even if you
were not opposed to that direction, makes it an unfeasible proposition.

Also, I'm not thinking its too mythical, sound/soc/intel/ is full of
audio DSP stuff, I think a newer version will just gain ART support.
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