linux-kernel - [PATCH 14/18] KVM: VMX: Avoid unnecessary vcpu_load()/vcpu

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Message-Id: <1177579338397-git-send-email-avi@qumranet.com>
Date:	Thu, 26 Apr 2007 12:22:14 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, Eddie Dong <eddie.dong@...el.com>,
	Avi Kivity <avi@...ranet.com>
Subject: [PATCH 14/18] KVM: VMX: Avoid unnecessary vcpu_load()/vcpu_put() cycles

From: Eddie Dong <eddie.dong@...el.com>

By checking if a reschedule is needed, we avoid dropping the vcpu.

[With changes by me, based on Anthony Liguori's observations]

Signed-off-by: Avi Kivity <avi@...ranet.com>
---
 drivers/kvm/kvm_main.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 03c0ee7..f535635 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1590,6 +1590,8 @@ static int set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
 
 void kvm_resched(struct kvm_vcpu *vcpu)
 {
+	if (!need_resched())
+		return;
 	vcpu_put(vcpu);
 	cond_resched();
 	vcpu_load(vcpu);
-- 
1.5.0.6

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