Commit 2086d320 authored May 17, 2016 by Christian Borntraeger Committed by Paolo Bonzini May 18, 2016

KVM: shrink halt polling even more for invalid wakeups



commit 3491caf2 ("KVM: halt_polling: provide a way to qualify
 wakeups during poll") added more aggressive shrinking of the
polling interval if the wakeup did not match some criteria. This
still allows to keep polling enabled if the polling time was
smaller that the current max poll time (block_ns <= vcpu->halt_poll_ns).
Performance measurement shows that even more aggressive shrinking
(shrink polling on any invalid wakeup) reduces absolute and relative
(to the workload) CPU usage even further.

Cc: David Matlack <dmatlack@google.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent c4a8de35

virt/kvm/kvm_main.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -2055,12 +2055,13 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
		out:
		block_ns = ktime_to_ns(cur) - ktime_to_ns(start);

		if (halt_poll_ns) {
		if (!vcpu_valid_wakeup(vcpu))
		shrink_halt_poll_ns(vcpu);
		else if (halt_poll_ns) {
		if (block_ns <= vcpu->halt_poll_ns)
		;
		/* we had a long block, shrink polling */
		else if (!vcpu_valid_wakeup(vcpu) \|\|
		(vcpu->halt_poll_ns && block_ns > halt_poll_ns))
		else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns)
		shrink_halt_poll_ns(vcpu);
		/* we had a short halt and our poll time is too small */
		else if (vcpu->halt_poll_ns < halt_poll_ns &&

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