rcu: Augment rcu_batch_end tracing for idle and callback state

The current rcu_batch_end event trace records only the name of the RCU
flavor and the total number of callbacks that remain queued on the
current CPU.  This is insufficient for testing and tuning the new
dyntick-idle RCU_FAST_NO_HZ code, so this commit adds idle state along
with whether or not any of the callbacks that were ready to invoke
at the beginning of rcu_do_batch() are still queued.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 29 insertions, 9 deletions

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index c75418c3ccb..d2d88bed891 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -461,27 +461,46 @@ TRACE_EVENT(rcu_invoke_kfree_callback,
 
 /*
  * Tracepoint for exiting rcu_do_batch after RCU callbacks have been
- * invoked.  The first argument is the name of the RCU flavor and
- * the second argument is number of callbacks actually invoked.
+ * invoked.  The first argument is the name of the RCU flavor,
+ * the second argument is number of callbacks actually invoked,
+ * the third argument (cb) is whether or not any of the callbacks that
+ * were ready to invoke at the beginning of this batch are still
+ * queued, the fourth argument (nr) is the return value of need_resched(),
+ * the fifth argument (iit) is 1 if the current task is the idle task,
+ * and the sixth argument (risk) is the return value from
+ * rcu_is_callbacks_kthread().
  */
 TRACE_EVENT(rcu_batch_end,
 
-        TP_PROTO(char *rcuname, int callbacks_invoked),
+        TP_PROTO(char *rcuname, int callbacks_invoked,
+                 bool cb, bool nr, bool iit, bool risk),
 
-        TP_ARGS(rcuname, callbacks_invoked),
+        TP_ARGS(rcuname, callbacks_invoked, cb, nr, iit, risk),
 
         TP_STRUCT__entry(
                 __field(char *, rcuname)
                 __field(int, callbacks_invoked)
+                __field(bool, cb)
+                __field(bool, nr)
+                __field(bool, iit)
+                __field(bool, risk)
         ),
 
         TP_fast_assign(
                 __entry->rcuname = rcuname;
                 __entry->callbacks_invoked = callbacks_invoked;
-        ),
-
-        TP_printk("%s CBs-invoked=%d",
-                  __entry->rcuname, __entry->callbacks_invoked)
+                __entry->cb = cb;
+                __entry->nr = nr;
+                __entry->iit = iit;
+                __entry->risk = risk;
+        ),
+
+        TP_printk("%s CBs-invoked=%d idle=%c%c%c%c",
+                  __entry->rcuname, __entry->callbacks_invoked,
+                  __entry->cb ? 'C' : '.',
+                  __entry->nr ? 'S' : '.',
+                  __entry->iit ? 'I' : '.',
+                  __entry->risk ? 'R' : '.')
 );
 
 /*
@@ -524,7 +543,8 @@ TRACE_EVENT(rcu_torture_read,
 #define trace_rcu_batch_start(rcuname, qlen, blimit) do { } while (0)
 #define trace_rcu_invoke_callback(rcuname, rhp) do { } while (0)
 #define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0)
-#define trace_rcu_batch_end(rcuname, callbacks_invoked) do { } while (0)
+#define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \
+        do { } while (0)
 #define trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
 
 #endif /* #else #ifdef CONFIG_RCU_TRACE */