[PATCH v2 3/3] KVM: trace kvm_halt_poll_ns grow/shrink

[Wanpeng Li <wanpeng.li@xxxxxxxxxxx>]

Tracepoint for dynamic halt_pool_ns, fired on every potential change.

Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
---
 include/trace/events/kvm.h | 30 ++++++++++++++++++++++++++++++
 virt/kvm/kvm_main.c        |  8 ++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index a44062d..75ddf80 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -356,6 +356,36 @@ TRACE_EVENT(
 		  __entry->address)
 );
 
+TRACE_EVENT(kvm_halt_poll_ns,
+	TP_PROTO(bool grow, unsigned int vcpu_id, int new, int old),
+	TP_ARGS(grow, vcpu_id, new, old),
+
+	TP_STRUCT__entry(
+		__field(bool, grow)
+		__field(unsigned int, vcpu_id)
+		__field(int, new)
+		__field(int, old)
+	),
+
+	TP_fast_assign(
+		__entry->grow           = grow;
+		__entry->vcpu_id        = vcpu_id;
+		__entry->new            = new;
+		__entry->old            = old;
+	),
+
+	TP_printk("vcpu %u: halt_pool_ns %d (%s %d)",
+			__entry->vcpu_id,
+			__entry->new,
+			__entry->grow ? "grow" : "shrink",
+			__entry->old)
+);
+
+#define trace_kvm_halt_poll_ns_grow(vcpu_id, new, old) \
+	trace_kvm_halt_poll_ns(true, vcpu_id, new, old)
+#define trace_kvm_halt_poll_ns_shrink(vcpu_id, new, old) \
+	trace_kvm_halt_poll_ns(false, vcpu_id, new, old)
+
 #endif
 
 #endif /* _TRACE_KVM_MAIN_H */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2a4962b..04f62e0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1957,13 +1957,21 @@ static unsigned int __shrink_halt_poll_ns(int val, int modifier, int minimum)
 
 static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
 {
+	int old = vcpu->halt_poll_ns;
+
 	vcpu->halt_poll_ns = __grow_halt_poll_ns(vcpu->halt_poll_ns);
+
+	trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, vcpu->halt_poll_ns, old);
 }
 
 static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
 {
+	int old = vcpu->halt_poll_ns;
+
 	vcpu->halt_poll_ns = __shrink_halt_poll_ns(vcpu->halt_poll_ns,
 			halt_poll_ns_shrink, halt_poll_ns);
+
+	trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, vcpu->halt_poll_ns, old);
 }
 
 static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
-- 
1.9.1

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