Re: [PATCH 1/2] KVM: mmu_notifier: Flush TLBs before releasing mmu_lock

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

(2012/02/10 16:52), Xiao Guangrong wrote:
> On 02/10/2012 02:28 PM, Takuya Yoshikawa wrote:
>
>> Other threads may process the same page in that small window and skip
>> TLB flush and then return before these functions do flush.
>>
>
>
> It is possible that flush tlb in mmu lock only when writeable
> spte is invalided? Sometimes, kvm_flush_remote_tlbs need
> long time to wait.
>

I am sorry but I don't see the point of adding yet another complexity
for that.


OK, let me clarify my position.

When I made this patch, I did a simple test to see if mmu notifier would
work normally after my patch applied:  I allocated large memory behind
the guest and made the host call mmu_notifier functions.

In that situation the host as a whole became slow, e.g. I saw really bad
response for some seconds.

In such a case, do you mind the additional time VCPU threads may have to
wait until the mmu notifier finishes the flush, only when they are trying
to take the mmu_lock?


	Takuya