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authorFrederic Weisbecker <fweisbec@gmail.com>2013-04-20 17:35:50 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2013-04-22 23:03:09 +0200
commitcb41a29076e9f95547da46578d5c8804f7b8845d (patch)
treeef6bcfbcd99ddbe366f1de94b6aa75da7c6ea55f
parent0637e029392386e6996f5d6574aadccee8315efa (diff)
downloadlinaro-lsk-cb41a29076e9f95547da46578d5c8804f7b8845d.tar.gz
nohz: Add basic tracing
It's not obvious to find out why the full dynticks subsystem doesn't always stop the tick: whether this is due to kthreads, posix timers, perf events, etc... These new tracepoints are here to help the user diagnose the failures and test this feature. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--include/trace/events/timer.h21
-rw-r--r--kernel/time/tick-sched.c19
2 files changed, 36 insertions, 4 deletions
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index 425bcfe56c6..f5eb53eb658 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -323,6 +323,27 @@ TRACE_EVENT(itimer_expire,
(int) __entry->pid, (unsigned long long)__entry->now)
);
+#ifdef CONFIG_NO_HZ_FULL
+TRACE_EVENT(tick_stop,
+
+ TP_PROTO(int success, char *error_msg),
+
+ TP_ARGS(success, error_msg),
+
+ TP_STRUCT__entry(
+ __field( int , success )
+ __string( msg, error_msg )
+ ),
+
+ TP_fast_assign(
+ __entry->success = success;
+ __assign_str(msg, error_msg);
+ ),
+
+ TP_printk("success=%s msg=%s", __entry->success ? "yes" : "no", __get_str(msg))
+);
+#endif
+
#endif /* _TRACE_TIMER_H */
/* This part must be outside protection */
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 12a900dbb81..85e05ab9825 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -28,6 +28,8 @@
#include "tick-internal.h"
+#include <trace/events/timer.h>
+
/*
* Per cpu nohz control structure
*/
@@ -153,14 +155,20 @@ static bool can_stop_full_tick(void)
{
WARN_ON_ONCE(!irqs_disabled());
- if (!sched_can_stop_tick())
+ if (!sched_can_stop_tick()) {
+ trace_tick_stop(0, "more than 1 task in runqueue\n");
return false;
+ }
- if (!posix_cpu_timers_can_stop_tick(current))
+ if (!posix_cpu_timers_can_stop_tick(current)) {
+ trace_tick_stop(0, "posix timers running\n");
return false;
+ }
- if (!perf_event_can_stop_tick())
+ if (!perf_event_can_stop_tick()) {
+ trace_tick_stop(0, "perf events running\n");
return false;
+ }
/* sched_clock_tick() needs us? */
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
@@ -168,8 +176,10 @@ static bool can_stop_full_tick(void)
* TODO: kick full dynticks CPUs when
* sched_clock_stable is set.
*/
- if (!sched_clock_stable)
+ if (!sched_clock_stable) {
+ trace_tick_stop(0, "unstable sched clock\n");
return false;
+ }
#endif
return true;
@@ -631,6 +641,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
ts->tick_stopped = 1;
+ trace_tick_stop(1, " ");
}
/*