diff options
| -rw-r--r-- | include/linux/kvm_host.h | 1 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 57 |
2 files changed, 48 insertions, 10 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 4721b11b922..3751ea0d1f9 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -235,6 +235,7 @@ struct kvm { #endif struct kvm_vcpu *vcpus[KVM_MAX_VCPUS]; atomic_t online_vcpus; + int last_boosted_vcpu; struct list_head vm_list; struct mutex lock; struct kvm_io_bus *buses[KVM_NR_BUSES]; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index bc8bfd15ab7..2dc53a6dc28 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1484,18 +1484,55 @@ void kvm_resched(struct kvm_vcpu *vcpu) } EXPORT_SYMBOL_GPL(kvm_resched); -void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu) +void kvm_vcpu_on_spin(struct kvm_vcpu *me) { - ktime_t expires; - DEFINE_WAIT(wait); - - prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE); - - /* Sleep for 100 us, and hope lock-holder got scheduled */ - expires = ktime_add_ns(ktime_get(), 100000UL); - schedule_hrtimeout(&expires, HRTIMER_MODE_ABS); + struct kvm *kvm = me->kvm; + struct kvm_vcpu *vcpu; + int last_boosted_vcpu = me->kvm->last_boosted_vcpu; + int yielded = 0; + int pass; + int i; - finish_wait(&vcpu->wq, &wait); + /* + * We boost the priority of a VCPU that is runnable but not + * currently running, because it got preempted by something + * else and called schedule in __vcpu_run. Hopefully that + * VCPU is holding the lock that we need and will release it. + * We approximate round-robin by starting at the last boosted VCPU. + */ + for (pass = 0; pass < 2 && !yielded; pass++) { + kvm_for_each_vcpu(i, vcpu, kvm) { + struct task_struct *task = NULL; + struct pid *pid; + if (!pass && i < last_boosted_vcpu) { + i = last_boosted_vcpu; + continue; + } else if (pass && i > last_boosted_vcpu) + break; + if (vcpu == me) + continue; + if (waitqueue_active(&vcpu->wq)) + continue; + rcu_read_lock(); + pid = rcu_dereference(vcpu->pid); + if (pid) + task = get_pid_task(vcpu->pid, PIDTYPE_PID); + rcu_read_unlock(); + if (!task) + continue; + if (task->flags & PF_VCPU) { + put_task_struct(task); + continue; + } + if (yield_to(task, 1)) { + put_task_struct(task); + kvm->last_boosted_vcpu = i; + yielded = 1; + break; + } + put_task_struct(task); + } + } } EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin); |