Commit 1e4ca26d authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Ingo Molnar
Browse files

tick/nohz: Change signal tick dependency to wake up CPUs of member tasks 



Rather than waking up all nohz_full CPUs on the system, only wake up
the target CPUs of member threads of the signal.

Reduces interruptions to nohz_full CPUs.

Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-8-frederic@kernel.org
parent 29721b85

include/linux/tick.h

+4 −4
Original line number Diff line number Diff line
@@ -211,7 +211,7 @@ extern void tick_nohz_dep_set_task(struct task_struct *tsk, 
				   enum tick_dep_bits bit);

extern void tick_nohz_dep_clear_task(struct task_struct *tsk,

				     enum tick_dep_bits bit);

extern void tick_nohz_dep_set_signal(struct signal_struct *signal,

extern void tick_nohz_dep_set_signal(struct task_struct *tsk,

				     enum tick_dep_bits bit);

extern void tick_nohz_dep_clear_signal(struct signal_struct *signal,

				       enum tick_dep_bits bit);
@@ -256,11 +256,11 @@ static inline void tick_dep_clear_task(struct task_struct *tsk, 
	if (tick_nohz_full_enabled())

		tick_nohz_dep_clear_task(tsk, bit);

}

static inline void tick_dep_set_signal(struct signal_struct *signal,

static inline void tick_dep_set_signal(struct task_struct *tsk,

				       enum tick_dep_bits bit)

{

	if (tick_nohz_full_enabled())

		tick_nohz_dep_set_signal(signal, bit);

		tick_nohz_dep_set_signal(tsk, bit);

}

static inline void tick_dep_clear_signal(struct signal_struct *signal,

					 enum tick_dep_bits bit)
@@ -288,7 +288,7 @@ static inline void tick_dep_set_task(struct task_struct *tsk, 
				     enum tick_dep_bits bit) { }

static inline void tick_dep_clear_task(struct task_struct *tsk,

				       enum tick_dep_bits bit) { }

static inline void tick_dep_set_signal(struct signal_struct *signal,

static inline void tick_dep_set_signal(struct task_struct *tsk,

				       enum tick_dep_bits bit) { }

static inline void tick_dep_clear_signal(struct signal_struct *signal,

					 enum tick_dep_bits bit) { }

kernel/time/posix-cpu-timers.c

+2 −2
Original line number Diff line number Diff line
@@ -523,7 +523,7 @@ static void arm_timer(struct k_itimer *timer, struct task_struct *p) 
	if (CPUCLOCK_PERTHREAD(timer->it_clock))

		tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);

	else

		tick_dep_set_signal(p->signal, TICK_DEP_BIT_POSIX_TIMER);

		tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);

}



/*
@@ -1358,7 +1358,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid, 
	if (*newval < *nextevt)

		*nextevt = *newval;



	tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER);

	tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);

}



static int do_cpu_nanosleep(const clockid_t which_clock, int flags,

kernel/time/tick-sched.c

+13 −2
Original line number Diff line number Diff line
@@ -444,9 +444,20 @@ EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task); 
 * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse

 * per process timers.

 */

void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits bit)

void tick_nohz_dep_set_signal(struct task_struct *tsk,

			      enum tick_dep_bits bit)

{

	tick_nohz_dep_set_all(&sig->tick_dep_mask, bit);

	int prev;

	struct signal_struct *sig = tsk->signal;



	prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask);

	if (!prev) {

		struct task_struct *t;



		lockdep_assert_held(&tsk->sighand->siglock);

		__for_each_thread(sig, t)

			tick_nohz_kick_task(t);

	}

}



void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)