Subject: Re: 2.4.x and SMP fails to compile (`current' undefined)
To: tleete@mountain.net (Tom Leete)
Date: Thu, 1 Feb 2001 10:50:56 +0000 (GMT)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), david@linux.com (David Ford),
        sfrost@snowman.net (Stephen Frost),
        linux-kernel@vger.kernel.org (LKML)
In-Reply-To: <3A7915AF.5C9C54CF@mountain.net> from "Tom Leete" at Feb 01, 2001 02:52:15 AM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

> > uninlining the code is too high a cost.
> 
> I question that. Athlon does branch prediction on call targets, function
> calls are cheap. 3dnow saves 25%-50% of cycles on a copy. How many function
> calls can be paid for with 1000 cycles or so?
> 
> My patch still inlines the standard string const_memcpy for the case of
> small known length.

We have a very large number of memcpy's of unknown short length (often in
interrupts) that are close to branches. A lot of

	if(foo==NULL)
		return
	memcpy(..

stuff for example.

Im more than happy for someone to do the benches and prove me wrong

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