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KVM: MMU: Avoid handling same rmap_pde in kvm_handle_hva_range()

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When we invalidate a THP page, we call the handler with the same
rmap_pde argument 512 times in the following loop:

  for each guest page in the range
    for each level
      unmap using rmap

This patch avoids these extra handler calls by changing the loop order
like this:

  for each level
    for each rmap in the range
      unmap using rmap

With the preceding patches in the patch series, this made THP page
invalidation more than 5 times faster on our x86 host: the host became
more responsive during swapping the guest's memory as a result.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Takuya Yoshikawa 2012-07-02 17:59:33 +09:00 committed by Marcelo Tosatti
parent f395302e09
commit bcd3ef5828
1 changed files with 18 additions and 10 deletions
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28
arch/x86/kvm/mmu.c
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@ -1277,7 +1277,7 @@ static int kvm_handle_hva_range(struct kvm *kvm,
kvm_for_each_memslot(memslot, slots) {
unsigned long hva_start, hva_end;
gfn_t gfn, gfn_end;
gfn_t gfn_start, gfn_end;
hva_start = max(start, memslot->userspace_addr);
hva_end = min(end, memslot->userspace_addr +
@ -1286,19 +1286,27 @@ static int kvm_handle_hva_range(struct kvm *kvm,
continue;
/*
* {gfn(page) | page intersects with [hva_start, hva_end)} =
* {gfn, gfn+1, ..., gfn_end-1}.
* {gfn_start, gfn_start+1, ..., gfn_end-1}.
*/
gfn = hva_to_gfn_memslot(hva_start, memslot);
gfn_start = hva_to_gfn_memslot(hva_start, memslot);
gfn_end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, memslot);
for (; gfn < gfn_end; ++gfn) {
for (j = PT_PAGE_TABLE_LEVEL;
j < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++j) {
unsigned long *rmapp;
for (j = PT_PAGE_TABLE_LEVEL;
j < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++j) {
unsigned long idx, idx_end;
unsigned long *rmapp;
rmapp = __gfn_to_rmap(gfn, j, memslot);
ret |= handler(kvm, rmapp, memslot, data);
}
/*
* {idx(page_j) | page_j intersects with
* [hva_start, hva_end)} = {idx, idx+1, ..., idx_end}.
*/
idx = gfn_to_index(gfn_start, memslot->base_gfn, j);
idx_end = gfn_to_index(gfn_end - 1, memslot->base_gfn, j);
rmapp = __gfn_to_rmap(gfn_start, j, memslot);
for (; idx <= idx_end; ++idx)
ret |= handler(kvm, rmapp++, memslot, data);
}
}