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KVM: Reduce atomic operations on vcpu->requests

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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>
This commit is contained in:
Avi Kivity 2010-05-10 13:08:26 +03:00
parent a8eeb04a44
commit 0719837c08
1 changed files with 6 additions and 1 deletions
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7
include/linux/kvm_host.h
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@ -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