Re: KVM performance

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Rusty Russell wrote:
>> The clever guest kernel will set the accessed bit (and the dirty bit on 
>> writable ptes) to avoid an rmw cycle by the hardware pagetable walker.
>>
>> [two instrumented runs later]
>>
>> Both Linux and Windows seem to do this optimization.
>>     
>
> Right.  This (trivial!) optimization wins lguest a good 10%:
>
> Before:
>     Time for one Copy-on-Write fault: 13622 nsec
>     Time to exec client once: 1085481 nsec
>     Time for one fork/exit/wait: 700796 nsec
> After:
>     Time for one Copy-on-Write fault: 12036 nsec
>     Time to exec client once: 969899 nsec
>     Time for one fork/exit/wait: 664601 nsec
>
>   

Another optimization is that we can stop having two parallel 
implementations of the same code.  I suggest we start thinking how to merge.

-- 
error compiling committee.c: too many arguments to function


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