Commit d1476937 authored Apr 23, 2010 by Takuya Yoshikawa Committed by Avi Kivity May 17, 2010

KVM: Remove test-before-set optimization for dirty bits

As Avi pointed out, testing bit part in mark_page_dirty() was important
in the days of shadow paging, but currently EPT and NPT has already become
common and the chance of faulting a page more that once per iteration is
small. So let's remove the test bit to avoid extra access.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

parent 03909187

virt/kvm/kvm_main.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -1192,8 +1192,6 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
		if (memslot && memslot->dirty_bitmap) {
		unsigned long rel_gfn = gfn - memslot->base_gfn;

		/* avoid RMW */
		if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap))
		generic___set_le_bit(rel_gfn, memslot->dirty_bitmap);
		}
		}

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