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    SubjectRe: [PATCH] KVM: VMX: Optimize flushing the PML buffer
    On Thu, Feb 4, 2021 at 2:51 PM Peter Xu <peterx@redhat.com> wrote:
    >
    > Hi, Ben,
    >
    > On Thu, Feb 04, 2021 at 02:19:59PM -0800, Ben Gardon wrote:
    > > The average time for each run demonstrated a strange bimodal distribution,
    > > with clusters around 2 seconds and 2.5 seconds. This may have been a
    > > result of vCPU migration between NUMA nodes.
    >
    > Have you thought about using numactl or similar technique to verify your idea
    > (force both vcpu threads binding, and memory allocations)?
    >
    > From the numbers it already shows improvements indeed, but just curious since
    > you raised this up. :)

    Frustratingly, the test machines I have don't have numactl installed
    but I've been meaning to add cpu pinning to the selftests perf tests
    anyway, so maybe this is a good reason to do it.

    >
    > > @@ -5707,13 +5708,18 @@ static void vmx_flush_pml_buffer(struct kvm_vcpu *vcpu)
    > > else
    > > pml_idx++;
    > >
    > > + memslots = kvm_vcpu_memslots(vcpu);
    > > +
    > > pml_buf = page_address(vmx->pml_pg);
    > > for (; pml_idx < PML_ENTITY_NUM; pml_idx++) {
    > > + struct kvm_memory_slot *memslot;
    > > u64 gpa;
    > >
    > > gpa = pml_buf[pml_idx];
    > > WARN_ON(gpa & (PAGE_SIZE - 1));
    > > - kvm_vcpu_mark_page_dirty(vcpu, gpa >> PAGE_SHIFT);
    > > +
    > > + memslot = __gfn_to_memslot(memslots, gpa >> PAGE_SHIFT);
    > > + mark_page_dirty_in_slot(vcpu->kvm, memslot, gpa >> PAGE_SHIFT);
    >
    > Since at it: make "gpa >> PAGE_SHIFT" a temp var too?

    That's a good idea, I'll try it.

    >
    > Thanks,
    >
    > --
    > Peter Xu
    >

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