rcu: Reduce rcutorture tracing
Currently, rcutorture traces every read-side access. This can be
problematic because even a two-minute rcutorture run on a two-CPU system
can generate 28,853,363 reads. Normally, only a failing read is of
interest, so this commit traces adjusts rcutorture's tracing to only
trace failing reads. The resulting event tracing records the time
and the ->completed value captured at the beginning of the RCU read-side
critical section, allowing correlation with other event-tracing messages.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
[ paulmck: Add fix to build problem located by Randy Dunlap based on
diagnosis by Steven Rostedt. ]
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3a35309..7d83f52 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1008,6 +1008,7 @@
config RCU_TRACE
bool "Enable tracing for RCU"
depends on DEBUG_KERNEL
+ select TRACE_CLOCK
help
This option provides tracing in RCU which presents stats
in debugfs for debugging RCU implementation.