Commit 026249ef authored Apr 20, 2013 by Frederic Weisbecker

perf: New helper to prevent full dynticks CPUs from stopping tick



Provide a new helper that help full dynticks CPUs to prevent
from stopping their tick in case there are events in the local
rotation list.

This way we make sure that perf_event_task_tick() is serviced
on demand.

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>
Cc: Stephane Eranian <eranian@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>

parent 12351ef8

include/linux/perf_event.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -799,6 +799,12 @@ static inline int __perf_event_disable(void *info) { return -1; }
		static inline void perf_event_task_tick(void) { }
		#endif

		#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_NO_HZ_FULL)
		extern bool perf_event_can_stop_tick(void);
		#else
		static inline bool perf_event_can_stop_tick(void) { return true; }
		#endif

		#define perf_output_put(handle, x) perf_output_copy((handle), &(x), sizeof(x))

		/*

kernel/events/core.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -2560,6 +2560,16 @@ done:
		list_del_init(&cpuctx->rotation_list);
		}

		#ifdef CONFIG_NO_HZ_FULL
		bool perf_event_can_stop_tick(void)
		{
		if (list_empty(&__get_cpu_var(rotation_list)))
		return true;
		else
		return false;
		}
		#endif

		void perf_event_task_tick(void)
		{
		struct list_head *head = &__get_cpu_var(rotation_list);