linux-kernel - [PATCH v2] KVM: Don't shrink/grow vCPU halt_poll

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Date:   Sun, 29 Sep 2019 09:06:56 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH v2] KVM: Don't shrink/grow vCPU halt_poll_ns if host side polling is disabled

From: Wanpeng Li <wanpengli@...cent.com>

Don't waste cycles to shrink/grow vCPU halt_poll_ns if host 
side polling is disabled.

Acked-by: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
v1 -> v2: 
 * fix coding style

 virt/kvm/kvm_main.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e6de315..9d5eed9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2359,20 +2359,23 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	kvm_arch_vcpu_unblocking(vcpu);
 	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
 
-	if (!vcpu_valid_wakeup(vcpu))
-		shrink_halt_poll_ns(vcpu);
-	else if (halt_poll_ns) {
-		if (block_ns <= vcpu->halt_poll_ns)
-			;
-		/* we had a long block, shrink polling */
-		else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns)
+	if (!kvm_arch_no_poll(vcpu)) {
+		if (!vcpu_valid_wakeup(vcpu)) {
 			shrink_halt_poll_ns(vcpu);
-		/* we had a short halt and our poll time is too small */
-		else if (vcpu->halt_poll_ns < halt_poll_ns &&
-			block_ns < halt_poll_ns)
-			grow_halt_poll_ns(vcpu);
-	} else
-		vcpu->halt_poll_ns = 0;
+		} else if (halt_poll_ns) {
+			if (block_ns <= vcpu->halt_poll_ns)
+				;
+			/* we had a long block, shrink polling */
+			else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns)
+				shrink_halt_poll_ns(vcpu);
+			/* we had a short halt and our poll time is too small */
+			else if (vcpu->halt_poll_ns < halt_poll_ns &&
+				block_ns < halt_poll_ns)
+				grow_halt_poll_ns(vcpu);
+		} else {
+			vcpu->halt_poll_ns = 0;
+		}
+	}
 
 	trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
 	kvm_arch_vcpu_block_finish(vcpu);
-- 
2.7.4