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Commit f0bc0a60 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
Browse files

vmscan: factor out kswapd sleeping logic from kswapd() 



Currently, kswapd() has deep nesting and is slightly hard to read.  Clean
this up.

Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c3f0da63

mm/vmscan.c

+46 −46
Original line number Diff line number Diff line
@@ -2371,6 +2371,50 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order) 
	return sc.nr_reclaimed;

}



static void kswapd_try_to_sleep(pg_data_t *pgdat, int order)

{

	long remaining = 0;

	DEFINE_WAIT(wait);



	if (freezing(current) || kthread_should_stop())

		return;



	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);



	/* Try to sleep for a short interval */

	if (!sleeping_prematurely(pgdat, order, remaining)) {

		remaining = schedule_timeout(HZ/10);

		finish_wait(&pgdat->kswapd_wait, &wait);

		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);

	}



	/*

	 * After a short sleep, check if it was a premature sleep. If not, then

	 * go fully to sleep until explicitly woken up.

	 */

	if (!sleeping_prematurely(pgdat, order, remaining)) {

		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);



		/*

		 * vmstat counters are not perfectly accurate and the estimated

		 * value for counters such as NR_FREE_PAGES can deviate from the

		 * true value by nr_online_cpus * threshold. To avoid the zone

		 * watermarks being breached while under pressure, we reduce the

		 * per-cpu vmstat threshold while kswapd is awake and restore

		 * them before going back to sleep.

		 */

		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);

		schedule();

		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);

	} else {

		if (remaining)

			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);

		else

			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);

	}

	finish_wait(&pgdat->kswapd_wait, &wait);

}



/*

 * The background pageout daemon, started as a kernel thread

 * from the init process.
@@ -2389,7 +2433,7 @@ static int kswapd(void *p) 
	unsigned long order;

	pg_data_t *pgdat = (pg_data_t*)p;

	struct task_struct *tsk = current;

	DEFINE_WAIT(wait);



	struct reclaim_state reclaim_state = {

		.reclaimed_slab = 0,

	};
@@ -2421,7 +2465,6 @@ static int kswapd(void *p) 
		unsigned long new_order;

		int ret;



		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);

		new_order = pgdat->kswapd_max_order;

		pgdat->kswapd_max_order = 0;

		if (order < new_order) {
@@ -2431,52 +2474,9 @@ static int kswapd(void *p) 
			 */

			order = new_order;

		} else {

			if (!freezing(current) && !kthread_should_stop()) {

				long remaining = 0;



				/* Try to sleep for a short interval */

				if (!sleeping_prematurely(pgdat, order, remaining)) {

					remaining = schedule_timeout(HZ/10);

					finish_wait(&pgdat->kswapd_wait, &wait);

					prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);

				}



				/*

				 * After a short sleep, check if it was a

				 * premature sleep. If not, then go fully

				 * to sleep until explicitly woken up

				 */

				if (!sleeping_prematurely(pgdat, order, remaining)) {

					trace_mm_vmscan_kswapd_sleep(pgdat->node_id);



					/*

					 * vmstat counters are not perfectly

					 * accurate and the estimated value

					 * for counters such as NR_FREE_PAGES

					 * can deviate from the true value by

					 * nr_online_cpus * threshold. To

					 * avoid the zone watermarks being

					 * breached while under pressure, we

					 * reduce the per-cpu vmstat threshold

					 * while kswapd is awake and restore

					 * them before going back to sleep.

					 */

					set_pgdat_percpu_threshold(pgdat,

						calculate_normal_threshold);

					schedule();

					set_pgdat_percpu_threshold(pgdat,

						calculate_pressure_threshold);

				} else {

					if (remaining)

						count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);

					else

						count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);

				}

			}



			kswapd_try_to_sleep(pgdat, order);

			order = pgdat->kswapd_max_order;

		}

		finish_wait(&pgdat->kswapd_wait, &wait);



		ret = try_to_freeze();

		if (kthread_should_stop())