nohz: Re-evaluate the tick from the scheduler IPI (ff442c51) · Commits · 戴 / test

The scheduler IPI is used by the scheduler to kick full dynticks CPUs asynchronously when more than one task are running or when a new timer list timer is enqueued. This way the destination CPU can decide to restart the tick to handle this new situation. Now let's call that kick in the scheduler IPI. (Reusing the scheduler IPI rather than implementing a new IPI was suggested by Peter Zijlstra a while ago) 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>

include/linux/tick.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -160,11 +160,13 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
		#ifdef CONFIG_NO_HZ_FULL
		extern void tick_nohz_init(void);
		extern int tick_nohz_full_cpu(int cpu);
		extern void tick_nohz_full_check(void);
		extern void tick_nohz_full_kick(void);
		extern void tick_nohz_full_kick_all(void);
		#else
		static inline void tick_nohz_init(void) { }
		static inline int tick_nohz_full_cpu(int cpu) { return 0; }
		static inline void tick_nohz_full_check(void) { }
		static inline void tick_nohz_full_kick(void) { }
		static inline void tick_nohz_full_kick_all(void) { }
		#endif

kernel/sched/core.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -1398,7 +1398,8 @@ static void sched_ttwu_pending(void)

		void scheduler_ipi(void)
		{
		if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
		if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()
		&& !tick_nohz_full_cpu(smp_processor_id()))
		return;

		/*
		@@ -1415,6 +1416,7 @@ void scheduler_ipi(void)
		* somewhat pessimize the simple resched case.
		*/
		irq_enter();
		tick_nohz_full_check();
		sched_ttwu_pending();

		/*

kernel/time/tick-sched.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -151,7 +151,7 @@ bool have_nohz_full_mask;
		* Re-evaluate the need for the tick on the current CPU
		* and restart it if necessary.
		*/
		static void tick_nohz_full_check(void)
		void tick_nohz_full_check(void)
		{
		/*
		* STUB for now, will be filled with the full tick stop/restart

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