linux-kernel - Re: [PATCH 00/15] cleanups and optimizations

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Message-ID: <alpine.DEB.2.02.1312172302560.31521@ionos.tec.linutronix.de>
Date:	Tue, 17 Dec 2013 23:11:50 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Arjan van de Ven <arjan@...ux.intel.com>, lenb@...nel.org,
	rjw@...ysocki.net, rui.zhang@...el.com,
	jacob.jun.pan@...ux.intel.com,
	Mike Galbraith <bitbucket@...ine.de>,
	Ingo Molnar <mingo@...nel.org>, hpa@...or.com,
	paulmck@...ux.vnet.ibm.com, John Stultz <john.stultz@...aro.org>,
	Andy Lutomirski <luto@...capital.net>,
	linux-kernel@...r.kernel.org, Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH 00/15] cleanups and optimizations

On Tue, 17 Dec 2013, Eliezer Tamir wrote:
> On 17/12/2013 17:13, Peter Zijlstra wrote:
> > On Tue, Dec 17, 2013 at 04:03:58PM +0200, Eliezer Tamir wrote:
> >>
> >> I'm not sure that subtracting the spin time is the optimal thing to do.
> >>
> >> The busy poll time is supposed to be limited to something less than 1ms.
> >> (I'm using 50us in most of my tests)
> >> This is typically orders of magnitude smaller than the poll timeout.
> >> Would it make more sense to just enforce a limit on poll time?
> >>
> >> What do you think?
> > 
> > I've no idea what people normally expect of select/poll wakeup
> > granularity but typically we already have 50us of timer slack, although
> > RT tasks go without this.
> 
> If RT tasks can't accept 50us of fuzziness, then the
> path of least astonishment would be to have fully accurate
> timekeeping, as you suggested. OK, so that's the plan.

No, the plan is to avoid busy loops in the first place.

Thanks,

	tglx
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