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KVM: Eliminate extra function calls in kvm_get_dirty_log_protect()

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When all bits in mask are not set,
kvm_arch_mmu_enable_log_dirty_pt_masked() has nothing to do.  But since
it needs to be called from the generic code, it cannot be inlined, and
a few function calls, two when PML is enabled, are wasted.

Since it is common to see many pages remain clean, e.g. framebuffers can
stay calm for a long time, it is worth eliminating this overhead.

Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Takuya Yoshikawa 2015-03-17 16:19:58 +09:00 committed by Marcelo Tosatti
parent faac245851
commit 58d2930f4e
1 changed files with 5 additions and 3 deletions
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8
virt/kvm/kvm_main.c
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@ -1053,9 +1053,11 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
mask = xchg(&dirty_bitmap[i], 0);
dirty_bitmap_buffer[i] = mask;
offset = i * BITS_PER_LONG;
kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot, offset,
mask);
if (mask) {
offset = i * BITS_PER_LONG;
kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
offset, mask);
}
}
spin_unlock(&kvm->mmu_lock);