From patchwork Mon Jan 3 21:30:03 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rik van Riel X-Patchwork-Id: 449141 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.3) with ESMTP id p03LVQKP024685 for ; Mon, 3 Jan 2011 21:31:26 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755246Ab1ACVaf (ORCPT ); Mon, 3 Jan 2011 16:30:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46442 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755114Ab1ACVad (ORCPT ); Mon, 3 Jan 2011 16:30:33 -0500 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id p03LUHe7009384 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 3 Jan 2011 16:30:17 -0500 Received: from annuminas.surriel.com (ovpn-113-70.phx2.redhat.com [10.3.113.70]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id p03LUAlI011529; Mon, 3 Jan 2011 16:30:15 -0500 Date: Mon, 3 Jan 2011 16:30:03 -0500 From: Rik van Riel To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Avi Kiviti , Srivatsa Vaddagiri , Peter Zijlstra , Mike Galbraith , Chris Wright Subject: [RFC -v3 PATCH 3/3] Subject: kvm: use yield_to instead of sleep in kvm_vcpu_on_spin Message-ID: <20110103163003.35354f1f@annuminas.surriel.com> In-Reply-To: <20110103162637.29f23c40@annuminas.surriel.com> References: <20110103162637.29f23c40@annuminas.surriel.com> Organization: Red Hat, Inc. Mime-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.3 (demeter1.kernel.org [140.211.167.41]); Mon, 03 Jan 2011 21:31:26 +0000 (UTC) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index c011ba3..ad3cb4a 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -185,6 +185,7 @@ 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 21f816c..5822246 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1878,18 +1878,44 @@ 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 = vcpu->task; + if (!pass && i < last_boosted_vcpu) { + i = last_boosted_vcpu; + continue; + } else if (pass && i > last_boosted_vcpu) + break; + if (vcpu == me) + continue; + if (!task) + continue; + if (waitqueue_active(&vcpu->wq)) + continue; + if (task->flags & PF_VCPU) + continue; + kvm->last_boosted_vcpu = i; + yielded = 1; + yield_to(task, 1); + break; + } + } } EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);