Commit 58d2930f authored Mar 17, 2015 by Takuya Yoshikawa Committed by Marcelo Tosatti Mar 18, 2015

KVM: Eliminate extra function calls in kvm_get_dirty_log_protect()



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>

parent faac2458

virt/kvm/kvm_main.c

+5 −3

Original line number	Original line	Diff line number	Diff line
	@@ -1053,9 +1053,11 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
	mask = xchg(&dirty_bitmap[i], 0);		mask = xchg(&dirty_bitmap[i], 0);
	dirty_bitmap_buffer[i] = mask;		dirty_bitmap_buffer[i] = mask;

			if (mask) {
	offset = i * BITS_PER_LONG;		offset = i * BITS_PER_LONG;
	kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot, offset,		kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
	mask);		offset, mask);
			}
	}		}

	spin_unlock(&kvm->mmu_lock);		spin_unlock(&kvm->mmu_lock);