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| author | Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> | 2010-04-23 17:48:35 +0900 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2010-05-17 12:19:13 +0300 |
| commit | d14769377a247d4e7b570592a090474c8a059938 (patch) | |
| tree | fd7e0de9712a29f99962b789ab3ab70a1338087f /virt | |
| parent | 039091875ce4629d83db64c055528e7b86337d50 (diff) | |
| download | lwn-d14769377a247d4e7b570592a090474c8a059938.tar.gz lwn-d14769377a247d4e7b570592a090474c8a059938.zip | |
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>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/kvm_main.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6dc940455e8b..9ab1a77941ef 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -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); } } |