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Commit 6a7b3dc3 authored by Rusty Russell's avatar Rusty Russell Committed by Ingo Molnar
Browse files

sched: convert nohz_cpu_mask to cpumask_var_t. 



Impact: (future) size reduction for large NR_CPUS.

Dynamically allocating cpumasks (when CONFIG_CPUMASK_OFFSTACK) saves
space for small nr_cpu_ids but big CONFIG_NR_CPUS.  cpumask_var_t
is just a struct cpumask for !CONFIG_CPUMASK_OFFSTACK.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6c99e9ad

include/linux/sched.h

+1 −1
Original line number Diff line number Diff line
@@ -249,7 +249,7 @@ extern void init_idle_bootup_task(struct task_struct *idle); 
extern int runqueue_is_locked(void);

extern void task_rq_unlock_wait(struct task_struct *p);



extern cpumask_t nohz_cpu_mask;

extern cpumask_var_t nohz_cpu_mask;

#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ)

extern int select_nohz_load_balancer(int cpu);

#else

kernel/rcuclassic.c

+1 −1
Original line number Diff line number Diff line
@@ -393,7 +393,7 @@ static void rcu_start_batch(struct rcu_ctrlblk *rcp) 
		 * unnecessarily.

		 */

		smp_mb();

		cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);

		cpumask_andnot(&rcp->cpumask, cpu_online_mask, nohz_cpu_mask);



		rcp->signaled = 0;

	}

kernel/sched.c

+5 −2
Original line number Diff line number Diff line
@@ -5870,9 +5870,9 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu) 
 * indicates which cpus entered this state. This is used

 * in the rcu update to wait only for active cpus. For system

 * which do not switch off the HZ timer nohz_cpu_mask should

 * always be CPU_MASK_NONE.

 * always be CPU_BITS_NONE.

 */

cpumask_t nohz_cpu_mask = CPU_MASK_NONE;

cpumask_var_t nohz_cpu_mask;



/*

 * Increase the granularity value when there are more CPUs,
@@ -8274,6 +8274,9 @@ void __init sched_init(void) 
	 */

	current->sched_class = &fair_sched_class;



	/* Allocate the nohz_cpu_mask if CONFIG_CPUMASK_OFFSTACK */

	alloc_bootmem_cpumask_var(&nohz_cpu_mask);



	scheduler_running = 1;

}

kernel/time/tick-sched.c

+5 −5
Original line number Diff line number Diff line
@@ -144,7 +144,7 @@ void tick_nohz_update_jiffies(void) 
	if (!ts->tick_stopped)

		return;



	cpu_clear(cpu, nohz_cpu_mask);

	cpumask_clear_cpu(cpu, nohz_cpu_mask);

	now = ktime_get();

	ts->idle_waketime = now;
@@ -283,7 +283,7 @@ void tick_nohz_stop_sched_tick(int inidle) 
	if ((long)delta_jiffies >= 1) {



		if (delta_jiffies > 1)

			cpu_set(cpu, nohz_cpu_mask);

			cpumask_set_cpu(cpu, nohz_cpu_mask);

		/*

		 * nohz_stop_sched_tick can be called several times before

		 * the nohz_restart_sched_tick is called. This happens when
@@ -296,7 +296,7 @@ void tick_nohz_stop_sched_tick(int inidle) 
				/*

				 * sched tick not stopped!

				 */

				cpu_clear(cpu, nohz_cpu_mask);

				cpumask_clear_cpu(cpu, nohz_cpu_mask);

				goto out;

			}
@@ -354,7 +354,7 @@ void tick_nohz_stop_sched_tick(int inidle) 
		 * softirq.

		 */

		tick_do_update_jiffies64(ktime_get());

		cpu_clear(cpu, nohz_cpu_mask);

		cpumask_clear_cpu(cpu, nohz_cpu_mask);

	}

	raise_softirq_irqoff(TIMER_SOFTIRQ);

out:
@@ -432,7 +432,7 @@ void tick_nohz_restart_sched_tick(void) 
	select_nohz_load_balancer(0);

	now = ktime_get();

	tick_do_update_jiffies64(now);

	cpu_clear(cpu, nohz_cpu_mask);

	cpumask_clear_cpu(cpu, nohz_cpu_mask);



	/*

	 * We stopped the tick in idle. Update process times would miss the