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Date: Wed, 04 Apr 2007 09:10:16 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Ingo Molnar <mingo@...e.hu>
CC: Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
lkml <linux-kernel@...r.kernel.org>
Subject: Re: [patch 04/17] Add pagetable accessors to pack and unpack pagetable
entries
Ingo Molnar wrote:
> sure. i simply took the middle numbers. But there's definitely a 'few
> percents' trend in the numbers.
>
Yep. I guess the thing that coloured my summary is that I found overhead
of unpatched paravirt_ops calls surprisingly small. I was really
expecting more like ~10% hit, but only null syscall approached that.
>>> this is not 'barely measurable' but 'BLOODY LARGE' overhead.
>>>
>> Yes. Fortunately there's a noticable difference between native and
>> unpatched paravirt, because it shows all the effort we put into
>> patching is worthwhile.
>>
>
> if only it were not such an ugly piece of code? ;)
>
Sigh, yes. I've cleaned it up a bit since the last post, and commented
it, but I couldn't do much with its essential ugliness. But I guess it
just got promoted from "ugly" to "ugly but necessary".
J
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