[Lguest] [PATCH 2/2] lguest: use get_user_pages_fast() instead of get_user_pages()

Rusty Russell rusty at rustcorp.com.au
Wed Jul 30 16:53:09 EST 2008


On Wednesday 30 July 2008 15:30:10 Nick Piggin wrote:
> On Wednesday 30 July 2008 14:39, Rusty Russell wrote:
> > 	Before: 5.93 seconds
> > 	After: 5.40 seconds
> >
> > (Counts of slow vs fastpath in this usage are 6092 and 2852462
> > respectively.)
> >
> > And more importantly for lguest, the code is simpler.
>
> Cool. That's actually a fairly significant straight-line performance
> improvement, given that the lguest processes are running one-at-a-time
> right? (and not contending on the locks or bouncing cachelines too much)

Yep.  I mean, the performance is abysmal either way (native for this is about 
10x faster), but it would be interesting to see kvm numbers as they have a 
more sophisticated shadow page table setup.  Not as trivial as lguest since 
they seem to use the mm sem to protect other things...

Cheers,
Rusty.



More information about the Lguest mailing list