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kvm: Record the preemption status of vcpus using preempt notifiers

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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.

Reviewed-by: Chegu Vinod <chegu_vinod@hp.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Raghavendra K T 2013-03-04 23:32:07 +05:30 committed by Gleb Natapov
parent 5da596078f
commit 3a08a8f9f0
2 changed files with 6 additions and 0 deletions
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1
include/linux/kvm_host.h
View file

@ -253,6 +253,7 @@ struct kvm_vcpu {
bool dy_eligible;
} spin_loop;
#endif
bool preempted;
struct kvm_vcpu_arch arch;
};

5
virt/kvm/kvm_main.c
View file

@ -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)
@ -2880,6 +2881,8 @@ 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);
}
@ -2889,6 +2892,8 @@ 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);
}