On 05/17/2016 10:49 AM, Christian Borntraeger wrote:
> commit 3491caf2755e ("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@xxxxxxxxxx>
> Cc: Wanpeng Li <kernellwp@xxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> CC: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> CC: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
> virt/kvm/kvm_main.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index fbd7698..dec1ed2 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -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);
^ hmpf. Small whitespace error. I can resend if wanted.
> + 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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