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

[Ingo Molnar <mingo@elte.hu>]

* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Ingo Molnar wrote:
> > the main metric we are interested in is the overhead for people who just 
> > want to run the non-patched native kernel that has CONFIG_PARAVIRT 
> > enabled (99%+ of the users at the moment), so the delta is:
> >
> >  null:              +12.0%
> >  null IO:            +7.5%
> >  stat:        within noise
> >  open/close:  within noise
> >  TCP:                ~5.0%
> >  signal install:      2.0%
> >  signal handle:       4.7%
> >  fork:                2.7%
> >  exec:                3.6%
> >  shell:               3.6%
> >   
>
> Hm, I don't think you can get this much precision out of these 
> numbers. I noticed larger variations from boot-to-boot running the 
> same test.

sure. i simply took the middle numbers. But there's definitely a 'few 
percents' trend in the numbers.

> > 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? ;)

	Ingo