Re: [PATCH v2 0/22] KVM: optimize for MMIO handled

Avi Kivity
2011-06-29T09:23:59Z

On 06/22/2011 05:27 PM, Xiao Guangrong wrote:
> In this version, we fix the bugs in the v1:
> - fix broken read emulation spans a page boundary
> - fix invalid spte point is got if we walk shadow page table
> out of the mmu lock
>
> And, we also introduce some rules to modify spte in this version,
> then it does not need to atomically clear/set spte on x86_32 host
> anymore, the performance report of x86_32 host is in the later section
>
> Avi,
>
> I have sampled the operation of lockless shadow page walking as below steps:
> - mark walk_shadow_page_get_mmio_spte as 'noinline'
> - do the netperf test, the client is on the guest(NIC is e1000) and the server
> is on the host, it can generate large press of mmio access
> - using perf to sample it, and the result of 'perf report' is attached
>
> The ratio of walk_shadow_page_get_mmio_spte is 0.09%, the ratio of handle_ept_misconfig
> is 0.11%, the ratio of handle_mmio_page_fault_common is 0.07%
>
> I think it is acceptable, your opinion?
>

Yes.

The patchset scares me, but it is nice work! Good optimization and good
clean up.

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