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    SubjectRe: [RFC][PATCH 0/9] rework KVM mmu_shrink() code
    On Wed, 2010-06-16 at 11:38 +0300, Avi Kivity wrote:
    > On 06/15/2010 04:55 PM, Dave Hansen wrote:
    > > These seem to boot and run fine. I'm running about 40 VMs at
    > > once, while doing "echo 3> /proc/sys/vm/drop_caches", and
    > > killing/restarting VMs constantly.
    > >
    > Will drop_caches actually shrink the kvm caches too? If so we probably
    > need to add that to autotest since it's a really good stress test for
    > the mmu.

    I'm completely sure. I crashed my machines several times this way
    during testing.

    > > Seems to be relatively stable, and seems to keep the numbers
    > > of kvm_mmu_page_header objects down.
    > >
    > That's no necessarily a good thing, those things are expensive to
    > recreate. Of course, when we do need to reclaim them, that should be
    > efficient.

    Oh, I meant that I didn't break the shrinker completely.

    > We also do a very bad job of selecting which page to reclaim. We need
    > to start using the accessed bit on sptes that point to shadow page
    > tables, and then look those up and reclaim unreferenced pages sooner.
    > With shadow paging there can be tons of unsync pages that are basically
    > unused and can be reclaimed at no cost to future runtime.

    Sounds like a good next step.

    -- Dave

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