| Message ID | 20210925005528.1145584-5-seanjc@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: Halt-polling fixes, cleanups and a new stat | expand |
On Fri, Sep 24, 2021 at 05:55:18PM -0700, Sean Christopherson wrote: > 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@google.com> Reviewed-by: David Matlack <dmatlack@google.com> > --- > 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 >
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)); }
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@google.com> --- virt/kvm/kvm_main.c | 35 ++++++++++++++++------------------- 1 file changed, 16 insertions(+), 19 deletions(-)