[PATCH] factor out kswapd sleeping logic from kswapd()

From: KOSAKI Motohiro
Date: Thu Dec 02 2010 - 20:48:41 EST


Currently, kswapd() function has deeper nest and it slightly harder to
read. cleanup it.

Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
mm/vmscan.c | 71 +++++++++++++++++++++++++++++++---------------------------
1 files changed, 38 insertions(+), 33 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8cc90d5..3ee33a8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2364,6 +2364,42 @@ out:
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);
+ 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.
@@ -2382,7 +2418,7 @@ 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,
};
@@ -2414,7 +2450,6 @@ 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) {
@@ -2424,39 +2459,9 @@ 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);
- 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())
--
1.6.5.2





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