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kvm: add halt-polling cpu usage stats

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Two new stats for exposing halt-polling cpu usage:
halt_poll_success_ns
halt_poll_fail_ns

Thus sum of these 2 stats is the total cpu time spent polling. "success"
means the VCPU polled until a virtual interrupt was delivered. "fail"
means the VCPU had to schedule out (either because the maximum poll time
was reached or it needed to yield the CPU).

To avoid touching every arch's kvm_vcpu_stat struct, only update and
export halt-polling cpu usage stats if we're on x86.

Exporting cpu usage as a u64 and in nanoseconds means we will overflow at
~500 years, which seems reasonably large.

Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Jon Cargille <jcargill@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>

Message-Id: <20200508182240.68440-1-jcargill@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Matlack
2020-05-08 11:22:40 -07:00
committed by Paolo Bonzini
parent 93dff2fed2
commit cb953129bf
10 changed files with 33 additions and 3 deletions
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18
virt/kvm/kvm_main.c
View File

@@ -2667,18 +2667,27 @@ out:
return ret;
}
static inline void
update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited)
{
if (waited)
vcpu->stat.halt_poll_fail_ns += poll_ns;
else
vcpu->stat.halt_poll_success_ns += poll_ns;
}
/*
* The vCPU has executed a HLT instruction with in-kernel mode enabled.
*/
void kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
ktime_t start, cur;
ktime_t start, cur, poll_end;
bool waited = false;
u64 block_ns;
kvm_arch_vcpu_blocking(vcpu);
start = cur = ktime_get();
start = cur = poll_end = ktime_get();
if (vcpu->halt_poll_ns && !kvm_arch_no_poll(vcpu)) {
ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
@@ -2694,7 +2703,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
++vcpu->stat.halt_poll_invalid;
goto out;
}
cur = ktime_get();
poll_end = cur = ktime_get();
} while (single_task_running() && ktime_before(cur, stop));
}
@@ -2714,6 +2723,9 @@ out:
kvm_arch_vcpu_unblocking(vcpu);
block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
update_halt_poll_stats(
vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
if (!kvm_arch_no_poll(vcpu)) {
if (!vcpu_valid_wakeup(vcpu)) {
shrink_halt_poll_ns(vcpu);