Re: [PATCH RFC 1/2] kvm: Record the preemption status of vcpus usingpreempt notifiers

[Raghavendra K T]

On 03/05/2013 08:49 PM, Chegu Vinod wrote:
> On 3/4/2013 10:02 AM, Raghavendra K T wrote:
> > From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
> >
> > Note that we mark as preempted only when vcpu's task state was
> > Running during preemption.
> >
> > Thanks Jiannan, Avi for preemption notifier ideas. Thanks Gleb, PeterZ
> > for their precious suggestions. Thanks Srikar for an idea on avoiding
> > rcu lock while checking task state that improved overcommit numbers.
> >
> > Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
> > ---
> >   include/linux/kvm_host.h |    1 +
> >   virt/kvm/kvm_main.c      |    5 +++++
> >   2 files changed, 6 insertions(+)
> >
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index cad77fe..0b31e1c 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -252,6 +252,7 @@ struct kvm_vcpu {
> >           bool dy_eligible;
> >       } spin_loop;
> >   #endif
> > +    bool preempted;
> >       struct kvm_vcpu_arch arch;
> >   };
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index adc68fe..83a804c 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -244,6 +244,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct
> > kvm *kvm, unsigned id)
> >       kvm_vcpu_set_in_spin_loop(vcpu, false);
> >       kvm_vcpu_set_dy_eligible(vcpu, false);
> > +    vcpu->preempted = false;
> >       r = kvm_arch_vcpu_init(vcpu);
> >       if (r < 0)
> > @@ -2902,6 +2903,8 @@ struct kvm_vcpu *preempt_notifier_to_vcpu(struct
> > preempt_notifier *pn)
> >   static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
> >   {
> >       struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
> > +    if (vcpu->preempted)
> > +        vcpu->preempted = false;
> >       kvm_arch_vcpu_load(vcpu, cpu);
> >   }
> > @@ -2911,6 +2914,8 @@ static void kvm_sched_out(struct
> > preempt_notifier *pn,
> >   {
> >       struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
> > +    if (current->state == TASK_RUNNING)
> > +        vcpu->preempted = true;
> >       kvm_arch_vcpu_put(vcpu);
> >   }
> >
> > .
> Reviewed-by: Chegu Vinod <chegu_vinod@xxxxxx>

Thank you Vinod.

Gleb, Marcelo,
 any comment, concern on the patches?


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