From: Michael Mueller <mimu@xxxxxxxxxxxxxxxxxx> Commit "kvm: Record the preemption status of vcpus using preempt notifiers" caused a performance regression on s390. It turned out that in the case that if a former sleeping cpu, that was woken up, this cpu is not a yield candidate since it gave up the cpu voluntarily. To retain this candiate its preempted flag is set during wakeup and interrupt delivery time. Significant performance measurement work and code analysis to solve this issue was provided by Mao Chuan Li and his team in Beijing. Signed-off-by: Michael Mueller <mimu@xxxxxxxxxxxxxxxxxx> Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> --- arch/s390/kvm/interrupt.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index 1848080..fff070b 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -505,6 +505,7 @@ enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer) struct kvm_vcpu *vcpu; vcpu = container_of(timer, struct kvm_vcpu, arch.ckc_timer); + vcpu->preempted = true; tasklet_schedule(&vcpu->arch.tasklet); return HRTIMER_NORESTART; @@ -732,6 +733,7 @@ static int __inject_vm(struct kvm *kvm, struct kvm_s390_interrupt_info *inti) atomic_set_mask(CPUSTAT_EXT_INT, li->cpuflags); if (waitqueue_active(li->wq)) wake_up_interruptible(li->wq); + kvm_get_vcpu(kvm, sigcpu)->preempted = true; spin_unlock_bh(&li->lock); unlock_fi: spin_unlock(&fi->lock); @@ -877,6 +879,7 @@ int kvm_s390_inject_vcpu(struct kvm_vcpu *vcpu, atomic_set_mask(CPUSTAT_EXT_INT, li->cpuflags); if (waitqueue_active(&vcpu->wq)) wake_up_interruptible(&vcpu->wq); + vcpu->preempted = true; spin_unlock_bh(&li->lock); mutex_unlock(&vcpu->kvm->lock); return 0; -- 1.8.4.2 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
