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@xxxxxxxxxx>
---
include/linux/kvm_host.h | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e706c1e..e478f3f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -642,7 +642,12 @@ 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
--
1.7.1
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