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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>
This commit is contained in:
Takuya Yoshikawa 2010-04-23 17:48:35 +09:00 committed by Avi Kivity
parent 039091875c
commit d14769377a
1 changed files with 1 additions and 3 deletions
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4
virt/kvm/kvm_main.c
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@ -1192,9 +1192,7 @@ 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);
generic___set_le_bit(rel_gfn, memslot->dirty_bitmap);
}
}