linux-kernel - Re: [PATCH 3.1?] x86: Remove useless stts/clts pair in __switch

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Message-ID: <20110725141339.GC3297@elte.hu>
Date:	Mon, 25 Jul 2011 16:13:39 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Lutomirski <luto@....edu>
Cc:	x86 <x86@...nel.org>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH 3.1?] x86: Remove useless stts/clts pair in __switch_to


* Andrew Lutomirski <luto@....edu> wrote:

> > Also, if you are tempted by the prospect of possibly enabling 
> > vector instructions for the x86 kernel, we could try that too, 
> > and get multiple speedups for the price of having to debug the 
> > tree only once ;-)
> 
> I'll play with it.  I have some other cleanup / speedup ideas, too, 
> and I'll see where they go.  Given that the kernel doesn't really 
> use floating-point math, I'm not sure that gcc will do much unless 
> we turn on -ftree-vectorize, and that's a little scary.

It's indeed scary - but as long as it boots it would allow some 
baseline figures to be estimated - is there any win, and if yes, how 
much. It might be a complete dud in the end.

Thanks,

	Ingo
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