linux-kernel - Re: [GIT pull] ntp updates for 2.6.31

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Message-ID: <20090623194916.GA18657@localhost>
Date:	Tue, 23 Jun 2009 21:49:16 +0200
From:	Miroslav Lichvar <mlichvar@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	John Stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [GIT pull] ntp updates for 2.6.31

On Tue, Jun 23, 2009 at 09:18:38PM +0200, Ingo Molnar wrote:
> 
> * Miroslav Lichvar <mlichvar@...hat.com> wrote:
> 
> > > > I'm not very familiar with the PPS API, is there something 
> > > > wrong with it?
> > > 
> > > The PPS patches i've seen just export IRQ timestamps to 
> > > user-space.
> > > 
> > > That is not very robust in my opinion when it comes to do time 
> > > approximations - to get quick, low-latency action and precise 
> > > measurements it's best to keep the critical path as short as 
> > > possible, and within a single source code repository: i.e. 
> > > within the kernel.
> > 
> > That's what kernel PPS discipline does, it will be probably 
> > included later. Its performance is an order or two better than the 
> > PLL/FLL discipline.
> 
> Is there some kernel patch i can look at?

It's in the old PPSkit patches for 2.4 kernels, function hardpps().

-- 
Miroslav Lichvar
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