linux-kernel - Re: [PATCH] Turn rdmsr, rdtsc into inline functions, clarify names

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Message-ID: <20060807192219.GA17521@suse.cz>
Date:	Mon, 7 Aug 2006 21:22:19 +0200
From:	Vojtech Pavlik <vojtech@...e.cz>
To:	Andi Kleen <ak@...e.de>
Cc:	Andreas Mohr <andi@...x01.fht-esslingen.de>,
	Dmitry Torokhov <dtor@...ightbb.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Turn rdmsr, rdtsc into inline functions, clarify names

On Mon, Aug 07, 2006 at 06:12:03PM +0200, Andi Kleen wrote:
> Vojtech Pavlik <vojtech@...e.cz> writes:
> 
> > On Mon, Aug 07, 2006 at 05:57:14PM +0200, Andi Kleen wrote:
> > > > That way a driver could use
> > > > 
> > > > 	if (gtod_cpu_cycles_needed <= 500)
> > > > 		gettimeofday();
> > > > 	else
> > > > 		funky_fast_workaround();
> > > 
> > > Sounds like overengineering to me. I prefer something simple.
> > 
> > I could as well benchmark gettimeofday() in the gameport init.
> 
> Except you can't because the only way to benchmark it would
> be to use gettimeofday already and then you don't know
> how much is overhead and what is the real time.
 
I run it for 1/10th of a second in a loop and see how many iterations
I've done.  That's enough to check if its fast enough to use in the
gameport routine. Less than 50k iterations and I can't use it.

-- 
Vojtech Pavlik
Director SuSE Labs
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