Move the halt-polling "success" and histogram stats update into the
dedicated helper to fix a discrepancy where the success/fail "time" stats
consider polling successful so long as the wait is avoided, but the main
"success" and histogram stats consider polling successful if and only if
a wake event was detected by the halt-polling loop.
Move halt_attempted_poll to the helper as well so that all the stats are
updated in a single location. While it's a bit odd to update the stat
well after the fact, practically speaking there's no meaningful advantage
to updating before polling.
Note, there is a functional change in addition to the success vs. fail
change. The histogram updates previously called ktime_get() instead of
using "cur". But that change is desirable as it means all the stats are
now updated with the same polling time, and avoids the extra ktime_get(),
which isn't expensive but isn't free either.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
virt/kvm/kvm_main.c | 35 ++++++++++++++++-------------------
1 file changed, 16 insertions(+), 19 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 12fe91a0a4c8..2ba22b68af3b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3202,12 +3202,23 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
ktime_t end, bool success)
{
+ struct kvm_vcpu_stat_generic *stats = &vcpu->stat.generic;
u64 poll_ns = ktime_to_ns(ktime_sub(end, start));
- if (success)
- vcpu->stat.generic.halt_poll_success_ns += poll_ns;
- else
- vcpu->stat.generic.halt_poll_fail_ns += poll_ns;
+ ++vcpu->stat.generic.halt_attempted_poll;
+
+ if (success) {
+ ++vcpu->stat.generic.halt_successful_poll;
+
+ if (!vcpu_valid_wakeup(vcpu))
+ ++vcpu->stat.generic.halt_poll_invalid;
+
+ stats->halt_poll_success_ns += poll_ns;
+ KVM_STATS_LOG_HIST_UPDATE(stats->halt_poll_success_hist, poll_ns);
+ } else {
+ stats->halt_poll_fail_ns += poll_ns;
+ KVM_STATS_LOG_HIST_UPDATE(stats->halt_poll_fail_hist, poll_ns);
+ }
}
/*
@@ -3227,30 +3238,16 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
if (do_halt_poll) {
ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
- ++vcpu->stat.generic.halt_attempted_poll;
do {
/*
* This sets KVM_REQ_UNHALT if an interrupt
* arrives.
*/
- if (kvm_vcpu_check_block(vcpu) < 0) {
- ++vcpu->stat.generic.halt_successful_poll;
- if (!vcpu_valid_wakeup(vcpu))
- ++vcpu->stat.generic.halt_poll_invalid;
-
- KVM_STATS_LOG_HIST_UPDATE(
- vcpu->stat.generic.halt_poll_success_hist,
- ktime_to_ns(ktime_get()) -
- ktime_to_ns(start));
+ if (kvm_vcpu_check_block(vcpu) < 0)
goto out;
- }
cpu_relax();
poll_end = cur = ktime_get();
} while (kvm_vcpu_can_poll(cur, stop));
-
- KVM_STATS_LOG_HIST_UPDATE(
- vcpu->stat.generic.halt_poll_fail_hist,
- ktime_to_ns(ktime_get()) - ktime_to_ns(start));
}
--
2.33.0.685.g46640cef36-goog
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
