From 9cac38dd5dc41c943d711b96f9755a29c8b854ea Mon Sep 17 00:00:00 2001 From: Michael Mueller <mimu@linux.vnet.ibm.com> Date: Wed, 26 Feb 2014 16:14:19 +0100 Subject: [PATCH] KVM/s390: Set preempted flag during vcpu wakeup and interrupt delivery 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@linux.vnet.ibm.com> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- 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 1848080c3f348..fff070bd0159c 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; -- GitLab