From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:29320 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726642AbgCMMks (ORCPT ); Fri, 13 Mar 2020 08:40:48 -0400 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02DCc22u126772 for ; Fri, 13 Mar 2020 08:40:47 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2yqyuwe8ch-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 13 Mar 2020 08:40:46 -0400 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 13 Mar 2020 12:40:44 -0000 From: Michael Mueller Subject: [PATCH] KVM: s390: pending interrupts are unlikely Date: Fri, 13 Mar 2020 13:40:30 +0100 Message-Id: <20200313124030.99834-1-mimu@linux.ibm.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: linux-s390@vger.kernel.org, kvm@vger.kernel.org Cc: borntraeger@de.ibm.com, frankja@linux.ibm.com, david@redhat.com, cohuck@redhat.com, heiko.carstens@de.ibm.com, gor@linux.ibm.com, Michael Mueller A statistical analysis shows that in most cases when deliverable_irqs() is called, no interrupts are pending. (see: early exit ratio) The data was sampled during an iperf3 run over virtio_net between one guest and the host. deliverable_irqs() called = 3145123 by kvm_s390_vcpu_has_irq() = 3005581 (95.56%) by kvm_arch_vcpu_runnable() = 3005578 (95.56%) by kvm_s390_handle_wait() = 1219331 (38.76%) by kvm_vcpu_check_block() = 2943565 (93.59%) by kvm_cpu_block(1) = 2826431 (89.86%) by kvm_cpu_block(2) = 117136 (3.72%) by kvm_arch_dy_runnable() = 0 (0%) by kvm_arch_setup_async_pf() = 0 (0%) by handle_stop() = 0 (0%) by kvm_s390_deliver_pending_interrupt() = 139542 (4.43%) irqs_delivered = (0:15917 1:61810 2:1 3:0 4:0 x:0) irqs_pending = (0:15917 1:61722 2:86 3:1 4:0 x:0) early exit = 3021787 (96.07%) pending irqs = 123237 (3.91%) Signed-off-by: Michael Mueller --- arch/s390/kvm/interrupt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index 028167d6eacd..c34d62b4209e 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -369,7 +369,7 @@ static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu) unsigned long active_mask; active_mask = pending_irqs(vcpu); - if (!active_mask) + if (likely(!active_mask)) return 0; if (psw_extint_disabled(vcpu)) -- 2.17.0