Re: [PATCH 0/4] Swapping

[Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Anthony Liguori wrote:
> Izik Eidus wrote:
>> this patchs allow the guest not shadowed memory to be swapped out.
>>
>> to make it the must effective you should run -kvm-shadow-memory 1 
>> (witch will make your machine slow)
>> with -kvm-shadow-memory 1,  3giga memory guest can get to be just 
>> 32mb on physical host!
>>
>> when not using -kvm-shadow-memory, i saw 4100mb machine getting to as 
>> low as 168mb on the physical host (not as bad as i thought it would 
>> be, and surely not as bad as it can be with 41mb of shadow pages :))
>>   
>
> So what exactly does this option do?  Is it really worth exposing it 
> as an option if it slows down guests so much?
>
> At least, a better name for the option would be nice.
>
> Regards,
>
> Anthony Liguori
-kvm-shadow-memory was included in kvm from version 46.
it control how much pages will be allocated to the shadow cache, (from 
version 46 the default is 2% of the system (so 4.1giga have about 80 mbs 
of shadow cache by default))
the problem is that each page that present at the shadow cache ( mmu 
pages ) cant be swapped out, so as lower as the number of shadow caches 
you have as more swappable will be
useful.

(this option (kvm-shadow-memory) was included to make it possible that 
as less as possible shadow cache memory will be deleated ( beacuse it 
have big overhead to lose this cache)

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