Re: [PATCH] KVM: Don't shrink/grow vCPU halt_poll_ns if host side polling is disabled

Wanpeng Li
2019-09-29T01:04:13Z

On Sat, 28 Sep 2019 at 01:24, Marcelo Tosatti <mtosatti@redhat.com> wrote:
>
> On Fri, Sep 27, 2019 at 04:27:02PM +0800, Wanpeng Li wrote:
> > 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
>
> Looks good.

I will add your ACK in v2.

Wanpeng