Re: [patch 04/17] Add pagetable accessors to pack and unpack pagetable entries

Jeremy Fitzhardinge
2007-04-04T16:10:35Z

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