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vmscan: factor out kswapd sleeping logic from kswapd()

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

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KOSAKI Motohiro 2011-01-13 15:45:50 -08:00 • committed by Linus Torvalds
parent c3f0da6315
commit f0bc0a60b1
1 changed files with 46 additions and 46 deletions
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92
mm/vmscan.c
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@ -2371,6 +2371,50 @@ out:
return sc.nr_reclaimed; 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 * The background pageout daemon, started as a kernel thread
* from the init process. * from the init process.
@ -2389,7 +2433,7 @@ static int kswapd(void *p)
unsigned long order; unsigned long order;
pg_data_t *pgdat = (pg_data_t*)p; pg_data_t *pgdat = (pg_data_t*)p;
struct task_struct *tsk = current; struct task_struct *tsk = current;
DEFINE_WAIT(wait);
struct reclaim_state reclaim_state = { struct reclaim_state reclaim_state = {
.reclaimed_slab = 0, .reclaimed_slab = 0,
}; };
@ -2421,7 +2465,6 @@ static int kswapd(void *p)
unsigned long new_order; unsigned long new_order;
int ret; int ret;
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
new_order = pgdat->kswapd_max_order; new_order = pgdat->kswapd_max_order;
pgdat->kswapd_max_order = 0; pgdat->kswapd_max_order = 0;
if (order < new_order) { if (order < new_order) {
@ -2431,52 +2474,9 @@ static int kswapd(void *p)
*/ */
order = new_order; order = new_order;
} else { } else {
if (!freezing(current) && !kthread_should_stop()) { kswapd_try_to_sleep(pgdat, order);
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);
}
}
order = pgdat->kswapd_max_order; order = pgdat->kswapd_max_order;
} }
finish_wait(&pgdat->kswapd_wait, &wait);
ret = try_to_freeze(); ret = try_to_freeze();
if (kthread_should_stop()) if (kthread_should_stop())