linux-kernel - Re: [PATCH] x86: Improve 64 bit __phys

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Date:	Wed, 10 Oct 2012 15:58:01 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	andi@...stfloor.org, linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] x86: Improve 64 bit __phys_addr call performance

> The second change was to streamline the code by making use of the carry flag
> on an add operation instead of performing a compare on a 64 bit value.  The
> advantage to this is that it allows us to reduce the overall size of the call.
> On my Xeon E5 system the entire __phys_addr inline call consumes 30 bytes and
> 5 instructions.  I also applied similar logic to the debug version of the
> function.  My testing shows that the debug version of the function with this
> patch applied is slightly faster than the non-debug version without the patch.

Looks good. Thanks. 

Probably should still split the callers though (or have a pa_symbol_fast
that does not do the check)

-Andi
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