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Date: Thu, 01 Feb 2001 02:52:15 -0500
From: Tom Leete <tleete@mountain.net>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: David Ford <david@linux.com>, Stephen Frost <sfrost@snowman.net>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: 2.4.x and SMP fails to compile (`current' undefined)
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Alan Cox wrote:
> 
> > It's not an incompatibility with the k7 chip, just bad code in
> > include/asm-i386/string.h. in_interrupt() cannot be called from there.
> 
> The string.h code was fine, someone came along and put in a ridiculous loop
> in the include dependancies and broke it. Nobody has had the time to untangle
> it cleanly since

Yes, bitrot. I don't see a rearrangement of system headers happening in 2.4.
I'm pretty sure if I committed such a patch it would have no measurable
lifetime.

> 
> > I have posted a patch here many times since last May. Most recent was
> > Saturday.
> 
> 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.

If I configure SMP for a UP box, performance is clearly not my first
concern. If I have a real SMP Athlon system, performance should not improve
by only using one processor.

How about we get it to build before we optimize it?

Regards,
Tom

-- 
The Daemons lurk and are dumb. -- Emerson
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