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| author | Frederic Weisbecker <fweisbec@gmail.com> | 2013-04-20 17:35:50 +0200 |
|---|---|---|
| committer | Frederic Weisbecker <fweisbec@gmail.com> | 2013-04-22 23:03:09 +0200 |
| commit | cb41a29076e9f95547da46578d5c8804f7b8845d (patch) | |
| tree | ef6bcfbcd99ddbe366f1de94b6aa75da7c6ea55f | |
| parent | nohz: Select wide RCU nocb for full dynticks (diff) | |
| download | linux-cb41a29076e9f95547da46578d5c8804f7b8845d.tar.xz linux-cb41a29076e9f95547da46578d5c8804f7b8845d.zip | |
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.h | 21 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 19 |
2 files changed, 36 insertions, 4 deletions
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h index 425bcfe56c62..f5eb53eb658f 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 12a900dbb819..85e05ab98253 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, " "); } /* |