cpuidle: haltpoll: Add trace points for guest_halt_poll_ns grow/shrink

Add trace points as are implemented in KVM host halt polling.
This helps tune guest halt polling params.
Signed-off-by: Eiichi Tsukata <eiichi.tsukata@nutanix.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/governors/haltpoll.c

@@ -19,6 +19,7 @@
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/kvm_para.h>
+#include <trace/events/power.h>
 
 static unsigned int guest_halt_poll_ns __read_mostly = 200000;
 module_param(guest_halt_poll_ns, uint, 0644);
@@ -90,6 +91,7 @@ static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
 		if (val > guest_halt_poll_ns)
 			val = guest_halt_poll_ns;
 
+		trace_guest_halt_poll_ns_grow(val, dev->poll_limit_ns);
 		dev->poll_limit_ns = val;
 	} else if (block_ns > guest_halt_poll_ns &&
 		   guest_halt_poll_allow_shrink) {
@@ -100,6 +102,7 @@ static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
 			val = 0;
 		else
 			val /= shrink;
+		trace_guest_halt_poll_ns_shrink(val, dev->poll_limit_ns);
 		dev->poll_limit_ns = val;
 	}
 }

include/trace/events/power.h

@@ -500,6 +500,35 @@ DEFINE_EVENT(dev_pm_qos_request, dev_pm_qos_remove_request,
 
 	TP_ARGS(name, type, new_value)
 );
+
+TRACE_EVENT(guest_halt_poll_ns,
+
+	TP_PROTO(bool grow, unsigned int new, unsigned int old),
+
+	TP_ARGS(grow, new, old),
+
+	TP_STRUCT__entry(
+		__field(bool, grow)
+		__field(unsigned int, new)
+		__field(unsigned int, old)
+	),
+
+	TP_fast_assign(
+		__entry->grow   = grow;
+		__entry->new    = new;
+		__entry->old    = old;
+	),
+
+	TP_printk("halt_poll_ns %u (%s %u)",
+		__entry->new,
+		__entry->grow ? "grow" : "shrink",
+		__entry->old)
+);
+
+#define trace_guest_halt_poll_ns_grow(new, old) \
+	trace_guest_halt_poll_ns(true, new, old)
+#define trace_guest_halt_poll_ns_shrink(new, old) \
+	trace_guest_halt_poll_ns(false, new, old)
 #endif /* _TRACE_POWER_H */
 
 /* This part must be outside protection */