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    SubjectRe: [PATCH v5 0/8] KVM: MMU: fast zap all shadow pages
    On 05/16/2013 10:36 PM, Takuya Yoshikawa wrote:
    > On Thu, 16 May 2013 20:17:45 +0800
    > Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> wrote:
    >
    >> Bechmark result:
    >> I have tested this patchset and the previous version that only zaps the
    >> pages linked on invalid slot's rmap. The benchmark is written by myself
    >> which has been attached, it writes large memory when do pci rom read.
    >>
    >> Host: Intel(R) Xeon(R) CPU X5690 @ 3.47GHz + 36G Memory
    >> Guest: 12 VCPU + 32G Memory
    >>
    >> Current code: This patchset Previous Version
    >> 2405434959 ns 2323016424 ns 2368810003 ns
    >>
    >> The interesting thing is, the previous version is slower than this patch,
    >> i guess the reason is that the former keeps lots of invalid pages in mmu
    >> which cause shadow page to be reclaimed due to used-pages > request-pages
    >> or host memory shrink.
    >
    > This patch series looks very nice!

    Thank you, Takuya!

    >
    > Minor issues may still need to be improved, but I really hope to see this
    > get merged during this cycle.
    >
    > [for the future] Do you think that postponing some zapping/freeing of
    > obsolete(already invalidated) pages to make_mmu_pages_available() time
    > can improve the situation more? -- say, for big guests.

    Yes, i think it can. :)

    We have made many efforts on this but still lack a straight way to
    achieve it.

    >
    > If accounting kept correct, make_mmu_pages_available() only needs to free
    > some obsolete pages instead of valid pages.
    >

    Yes.




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