From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Date: Mon, 4 Mar 2013 18:02:27 +0000 (+0530)
Subject: kvm: Iterate over only vcpus that are preempted
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=7bc7ae25b1438bb9fe1f176b951d758789847640;p=openwrt%2Fstaging%2Fblogic.git

kvm: Iterate over only vcpus that are preempted

This helps in filtering out the eligible candidates further and
thus potentially helps in quickly allowing preempted lockholders to run.
Note that if a vcpu was spinning during preemption we filter them
by checking whether they are preempted due to pause loop exit.

Reviewed-by: Chegu Vinod <chegu_vinod@hp.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
---

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 470f2bc8205a..ff7154188b5f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1768,6 +1768,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
 				continue;
 			} else if (pass && i > last_boosted_vcpu)
 				break;
+			if (!ACCESS_ONCE(vcpu->preempted))
+				continue;
 			if (vcpu == me)
 				continue;
 			if (waitqueue_active(&vcpu->wq))