Re: [PATCH][UPDATE] Shortcut MSR save/restore for lightweight VM Exit

Dong, Eddie
2007-05-08T11:51:54Z

Avi Kivity wrote:
> Dong, Eddie wrote:
>> This patch reduce the VM Exit handling cost continuously
>> for those lightweight VM Exit which occupies 93% of VM Exit in
>> KB case if 64 bits OS has similar situation with 32 bits. In my old
>> machine, I saw 20% performance increasement of KB within 64 bits
>> RHEL5 guest and flat for 32bits FC5.
>> There are still some room to improvment here, but this one
>> focus on basic MSR save/restore framework only for now and leave
>> future to opitmize specific MSRs like GS_BASE etc.
>> thx,eddie
>>
>> Signed-off-by: Yaozu(Eddie) Dong Eddie.Dong-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org
>>
>> against 5cf48c367dec74ba8553c53ed332cd075fa38b88
>>
>>
>
> Much has changed. Please rebase against HEAD.
>
> Also, there have been a lot of regressions with the msr code. Please

The previous MSR optmization patch only focus on heavyweight VM exit
path, with 5cf48c367dec74ba8553c53ed332cd075fa38b88, it doesn't cover
the major path.
This patch remove save/restore for most HW MSRs, which imply to both
heavy weight
and light weight VM Exit path, to heavyweight VM Exit only SW path.

> test on i386 and on Core Duo i386 (which is a little different) in
> addition to the regular x86_64.

I have tested this on I386, it is exactly same since software save MSRs
are 0 and HW saved is 1, which is same with before. I will test on
Conroe/Woodcrest to see the exactly performance gain with KB.