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From: Wanpeng Li <kernellwp@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Subject: [PATCH v4 1/2] KVM: X86: Less kvmclock sync induced vmexits after VM boots
Date: Tue, 18 Feb 2020 09:17:09 +0800	[thread overview]
Message-ID: <1581988630-19182-1-git-send-email-wanpengli@tencent.com> (raw)

From: Wanpeng Li <wanpengli@tencent.com>

In the progress of vCPUs creation, it queues a kvmclock sync worker to the global 
workqueue before each vCPU creation completes. Each worker will be scheduled 
after 300 * HZ delay and request a kvmclock update for all vCPUs and kick them 
out. This is especially worse when scaling to large VMs due to a lot of vmexits. 
Just one worker as a leader to trigger the kvmclock sync request for all vCPUs is 
enough.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
v3 -> v4:
 * check vcpu->vcpu_idx

 arch/x86/kvm/x86.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fb5d64e..d0ba2d4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9390,8 +9390,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 	if (!kvmclock_periodic_sync)
 		return;
 
-	schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
-					KVMCLOCK_SYNC_PERIOD);
+	if (vcpu->vcpu_idx == 0)
+		schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
+						KVMCLOCK_SYNC_PERIOD);
 }
 
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
-- 
2.7.4


             reply	other threads:[~2020-02-18  1:19 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-18  1:17 Wanpeng Li [this message]
2020-02-18  1:17 ` [PATCH RESEND v4 2/2] KVM: nVMX: Hold KVM's srcu lock when syncing vmcs12->shadow Wanpeng Li
2020-02-18 14:54 ` [PATCH v4 1/2] KVM: X86: Less kvmclock sync induced vmexits after VM boots Vitaly Kuznetsov
2020-02-18 15:33   ` Paolo Bonzini
2020-02-18 16:29     ` Vitaly Kuznetsov
2020-02-18 16:31       ` Paolo Bonzini
2020-02-19  0:32   ` Wanpeng Li

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