Commit 0719837c authored May 10, 2010 by Avi Kivity

KVM: Reduce atomic operations on vcpu->requests



Usually the vcpu->requests bitmap is sparse, so a test_and_clear_bit() for
each request generates a large number of unneeded atomics if a bit is set.

Replace with a separate test/clear sequence.  This is safe since there is
no clear_bit() outside the vcpu thread.

Signed-off-by: Avi Kivity <avi@redhat.com>

parent a8eeb04a

include/linux/kvm_host.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -636,7 +636,12 @@ static inline bool kvm_make_check_request(int req, struct kvm_vcpu *vcpu)

		static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
		{
		return test_and_clear_bit(req, &vcpu->requests);
		if (test_bit(req, &vcpu->requests)) {
		clear_bit(req, &vcpu->requests);
		return true;
		} else {
		return false;
		}
		}

		#endif