When we have "block_ns > halt_poll_ns" and "block_ns < max_halt_poll_ns",
then "halt_poll_ns < max_halt_poll_ns" is true, so we can drop this extra
condition.
We want to make sure halt_poll_ns is not zero before shrinking it. Put
the condition in shrinking primitive can make code clearer.
None functional change.
Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
---
Documentation/virt/kvm/halt-polling.rst | 21 ++++++++++-----------
virt/kvm/kvm_main.c | 11 ++++++-----
2 files changed, 16 insertions(+), 16 deletions(-)
diff --git a/Documentation/virt/kvm/halt-polling.rst b/Documentation/virt/kvm/halt-polling.rst
index 4922e4a15f18..d9f699395a7f 100644
--- a/Documentation/virt/kvm/halt-polling.rst
+++ b/Documentation/virt/kvm/halt-polling.rst
@@ -47,17 +47,16 @@ Thus this is a per vcpu (or vcore) value.
During polling if a wakeup source is received within the halt polling interval,
the interval is left unchanged. In the event that a wakeup source isn't
received during the polling interval (and thus schedule is invoked) there are
-two options, either the polling interval and total block time[0] were less than
-the global max polling interval (see module params below), or the total block
-time was greater than the global max polling interval.
-
-In the event that both the polling interval and total block time were less than
-the global max polling interval then the polling interval can be increased in
-the hope that next time during the longer polling interval the wake up source
-will be received while the host is polling and the latency benefits will be
-received. The polling interval is grown in the function grow_halt_poll_ns() and
-is multiplied by the module parameters halt_poll_ns_grow and
-halt_poll_ns_grow_start.
+two options, either the total block time[0] were less than the global max
+polling interval (see module params below), or the total block time was greater
+than the global max polling interval.
+
+In the event that the total block time were less than the global max polling
+interval then the polling interval can be increased in the hope that next time
+during the longer polling interval the wake up source will be received while the
+host is polling and the latency benefits will be received. The polling interval
+is grown in the function grow_halt_poll_ns() and is multiplied by the module
+parameters halt_poll_ns_grow and halt_poll_ns_grow_start.
In the event that the total block time was greater than the global max polling
interval then the host will never poll for long enough (limited by the global
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6b4feb92dc79..13a9996c4ccb 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2906,6 +2906,9 @@ static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
unsigned int old, val, shrink;
old = val = vcpu->halt_poll_ns;
+ if (!old)
+ return;
+
shrink = READ_ONCE(halt_poll_ns_shrink);
if (shrink == 0)
val = 0;
@@ -3003,12 +3006,10 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
if (block_ns <= vcpu->halt_poll_ns)
;
/* we had a long block, shrink polling */
- else if (vcpu->halt_poll_ns &&
- block_ns > vcpu->kvm->max_halt_poll_ns)
+ else if (block_ns > vcpu->kvm->max_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 < vcpu->kvm->max_halt_poll_ns &&
- block_ns < vcpu->kvm->max_halt_poll_ns)
+ /* we had a short block, grow polling */
+ else if (block_ns < vcpu->kvm->max_halt_poll_ns)
grow_halt_poll_ns(vcpu);
} else {
vcpu->halt_poll_ns = 0;
--
2.19.1
