Messages in this thread Patch in this message | | | Date | Thu, 28 Jun 2012 11:02:35 +0900 | From | Takuya Yoshikawa <> | Subject | [PATCH 6/6] 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.
Note: in the new code we could not use trace_kvm_age_page(), so we just dropped the point from kvm_handle_hva_range().
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> --- arch/x86/kvm/mmu.c | 37 +++++++++++++++++++------------------ 1 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 477b3da..524f7c0 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1192,8 +1192,7 @@ static int kvm_handle_hva_range(struct kvm *kvm, unsigned long data)) { int j; - int ret; - int retval = 0; + int ret = 0; struct kvm_memslots *slots; struct kvm_memory_slot *memslot; @@ -1201,7 +1200,7 @@ 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 + @@ -1210,29 +1209,31 @@ 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) { - ret = 0; + for (j = PT_PAGE_TABLE_LEVEL; + j < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++j) { + unsigned long idx, idx_end; + unsigned long *rmapp; - for (j = PT_PAGE_TABLE_LEVEL; - j < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++j) { - unsigned long *rmapp; + /* + * {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, j, memslot); - ret |= handler(kvm, rmapp, data); - } - trace_kvm_age_page(memslot->userspace_addr + - (gfn - memslot->base_gfn) * PAGE_SIZE, - memslot, ret); - retval |= ret; + rmapp = __gfn_to_rmap(gfn_start, j, memslot); + + for (; idx <= idx_end; ++idx) + ret |= handler(kvm, rmapp++, data); } } - return retval; + return ret; } static int kvm_handle_hva(struct kvm *kvm, unsigned long hva, -- 1.7.5.4
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