Re: [RFC] KVM MMU: improve large munmap efficiency

[Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>]

(2012/01/27 9:59), Takuya Yoshikawa wrote:

>> We have seen delays of over 30 seconds doing a large (128GB) unmap.
>>
>> It'd be nicer to check if the amount of work to be done by the entire
>> flush is less than the work to be done iterating over each HVA page,
>> but that information isn't currently available to the arch-
>> independent part of KVM.
>
> Using the number of (active) shadow pages may be one way.
>
> See kvm->arch.n_used_mmu_pages.

Ah, sorry, you are looking for arch independent information.

>
>
>>
>> Better ideas would be most welcome ;-)
>
>
> I will soon, this weekend if possible, send a patch series which may
> result in speeding up kvm_unmap_hva() loop.

... and I also need to check if my work can be naturally implemented by
arch independent manner.

	Takuya

>
> Though my work has been done for optimizing a different thing, dirty
> logging, I think this loop will also be optimized.
>
> I have checked that dirty logging improved significantly,
> so hope that your case will also.
>
> So, in addition to your patch, please see to what extent my patch series
> will help your case, if possible.
>
> Thanks,
> Takuya