[PATCH v2 6/6] KVM: stats: Add halt polling related histogram stats

Add three log histogram stats to record the distribution of time spent
on successful polling, failed polling and VCPU wait.
halt_poll_success_hist: Distribution of spent time for a successful poll.
halt_poll_fail_hist: Distribution of spent time for a failed poll.
halt_wait_hist: Distribution of time a VCPU has spent on waiting.

Signed-off-by: Jing Zhang <[email protected]>
---
 arch/powerpc/kvm/book3s_hv.c | 16 ++++++++++++++--
 include/linux/kvm_host.h     | 13 ++++++++++++-
 include/linux/kvm_types.h    |  5 +++++
 virt/kvm/kvm_main.c          | 12 ++++++++++++
 4 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 92698a5e54fd..c75a5f46d31d 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4146,17 +4146,29 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc)
 	if (do_sleep) {
 		vc->runner->stat.generic.halt_wait_ns + 			ktime_to_ns(cur) - ktime_to_ns(start_wait);
+		halt_poll_hist_update(
+				vc->runner->stat.generic.halt_wait_hist,
+				ktime_to_ns(cur) - ktime_to_ns(start_wait));
 		/* Attribute failed poll time */
-		if (vc->halt_poll_ns)
+		if (vc->halt_poll_ns) {
 			vc->runner->stat.generic.halt_poll_fail_ns + 				ktime_to_ns(start_wait) -
 				ktime_to_ns(start_poll);
+			halt_poll_hist_update(
+				vc->runner->stat.generic.halt_poll_fail_hist,
+				ktime_to_ns(start_wait) -
+				ktime_to_ns(start_poll));
+		}
 	} else {
 		/* Attribute successful poll time */
-		if (vc->halt_poll_ns)
+		if (vc->halt_poll_ns) {
 			vc->runner->stat.generic.halt_poll_success_ns + 				ktime_to_ns(cur) -
 				ktime_to_ns(start_poll);
+			halt_poll_hist_update(
+				vc->runner->stat.generic.halt_poll_success_hist,
+				ktime_to_ns(cur) - ktime_to_ns(start_poll));
+		}
 	}
 
 	/* Adjust poll time */
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2414f3c7e6f7..e0db0216e627 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1370,7 +1370,13 @@ struct _kvm_stats_desc {
 	STATS_DESC_COUNTER(VCPU_GENERIC, halt_wakeup),			       \
 	STATS_DESC_TIME_NSEC(VCPU_GENERIC, halt_poll_success_ns),	       \
 	STATS_DESC_TIME_NSEC(VCPU_GENERIC, halt_poll_fail_ns),		       \
-	STATS_DESC_TIME_NSEC(VCPU_GENERIC, halt_wait_ns)
+	STATS_DESC_TIME_NSEC(VCPU_GENERIC, halt_wait_ns),		       \
+	STATS_DESC_LOGHIST_TIME_NSEC(VCPU_GENERIC, halt_poll_success_hist,     \
+			HALT_POLL_HIST_COUNT),				       \
+	STATS_DESC_LOGHIST_TIME_NSEC(VCPU_GENERIC, halt_poll_fail_hist,	       \
+			HALT_POLL_HIST_COUNT),				       \
+	STATS_DESC_LOGHIST_TIME_NSEC(VCPU_GENERIC, halt_wait_hist,	       \
+			HALT_POLL_HIST_COUNT)
 
 extern struct dentry *kvm_debugfs_dir;
 
@@ -1387,6 +1393,11 @@ extern const struct _kvm_stats_desc kvm_vm_stats_desc[];
 extern const struct kvm_stats_header kvm_vcpu_stats_header;
 extern const struct _kvm_stats_desc kvm_vcpu_stats_desc[];
 
+static inline void halt_poll_hist_update(u64 *hist, u64 value)
+{
+	kvm_stats_log_hist_update(hist, HALT_POLL_HIST_COUNT, value);
+}
+
 #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
 static inline int mmu_notifier_retry(struct kvm *kvm, unsigned long mmu_seq)
 {
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index d70f8f475da1..e073cfcabf8c 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -91,6 +91,8 @@ struct kvm_mmu_memory_cache {
 #define LOGHIST_BUCKET_COUNT_LARGE		32
 #define LOGHIST_BUCKET_COUNT_XLARGE		64
 
+#define HALT_POLL_HIST_COUNT			LOGHIST_BUCKET_COUNT_LARGE
+
 struct kvm_vm_stat_generic {
 	u64 remote_tlb_flush;
 };
@@ -103,6 +105,9 @@ struct kvm_vcpu_stat_generic {
 	u64 halt_poll_success_ns;
 	u64 halt_poll_fail_ns;
 	u64 halt_wait_ns;
+	u64 halt_poll_success_hist[HALT_POLL_HIST_COUNT];
+	u64 halt_poll_fail_hist[HALT_POLL_HIST_COUNT];
+	u64 halt_wait_hist[HALT_POLL_HIST_COUNT];
 };
 
 #define KVM_STATS_NAME_SIZE	48
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 88bf17e7bf51..5fcdffd7d66a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3108,12 +3108,22 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 				++vcpu->stat.generic.halt_successful_poll;
 				if (!vcpu_valid_wakeup(vcpu))
 					++vcpu->stat.generic.halt_poll_invalid;
+
+				halt_poll_hist_update(
+				      vcpu->stat.generic.halt_poll_success_hist,
+				      ktime_to_ns(ktime_get()) -
+				      ktime_to_ns(start));
 				goto out;
 			}
 			poll_end = cur = ktime_get();
 		} while (kvm_vcpu_can_poll(cur, stop));
+
+		halt_poll_hist_update(
+				vcpu->stat.generic.halt_poll_fail_hist,
+				ktime_to_ns(ktime_get()) - ktime_to_ns(start));
 	}
 
+
 	prepare_to_rcuwait(&vcpu->wait);
 	for (;;) {
 		set_current_state(TASK_INTERRUPTIBLE);
@@ -3129,6 +3139,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	if (waited) {
 		vcpu->stat.generic.halt_wait_ns + 			ktime_to_ns(cur) - ktime_to_ns(poll_end);
+		halt_poll_hist_update(vcpu->stat.generic.halt_wait_hist,
+				ktime_to_ns(cur) - ktime_to_ns(poll_end));
 	}
 out:
 	kvm_arch_vcpu_unblocking(vcpu);
-- 
2.32.0.402.g57bb445576-goog