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Subject[PATCH] KVM: Don't shrink/grow vCPU halt_poll_ns if host side polling is disabled
Date
From: Wanpeng Li <wanpengli@tencent.com>

Don't waste cycles to shrink/grow vCPU halt_poll_ns if host
side polling is disabled.

Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
virt/kvm/kvm_main.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e6de315..b368be4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2359,20 +2359,22 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
kvm_arch_vcpu_unblocking(vcpu);
block_ns = ktime_to_ns(cur) - ktime_to_ns(start);

- 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->halt_poll_ns && block_ns > halt_poll_ns)
+ if (!kvm_arch_no_poll(vcpu)) {
+ if (!vcpu_valid_wakeup(vcpu))
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 &&
- block_ns < halt_poll_ns)
- grow_halt_poll_ns(vcpu);
- } else
- vcpu->halt_poll_ns = 0;
+ else if (halt_poll_ns) {
+ if (block_ns <= vcpu->halt_poll_ns)
+ ;
+ /* we had a long block, shrink polling */
+ 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 &&
+ block_ns < halt_poll_ns)
+ grow_halt_poll_ns(vcpu);
+ } else
+ vcpu->halt_poll_ns = 0;
+ }

trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
kvm_arch_vcpu_block_finish(vcpu);
--
2.7.4
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