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authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>2009-12-14 17:58:55 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-15 08:53:16 -0800
commitbb3ab596832b920c703d1aea1ce76d69c0f71fb7 (patch)
tree048162bf5081e7bd9802eba012e8b680a4444da8 /mm
parentf50de2d3811081957156b5d736778799379c29de (diff)
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vmscan: stop kswapd waiting on congestion when the min watermark is not being met
If reclaim fails to make sufficient progress, the priority is raised. Once the priority is higher, kswapd starts waiting on congestion. However, if the zone is below the min watermark then kswapd needs to continue working without delay as there is a danger of an increased rate of GFP_ATOMIC allocation failure. This patch changes the conditions under which kswapd waits on congestion by only going to sleep if the min watermarks are being met. [mel@csn.ul.ie: add stats to track how relevant the logic is] [mel@csn.ul.ie: make kswapd only check its own zones and rename the relevant counters] Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/vmscan.c38
-rw-r--r--mm/vmstat.c5
2 files changed, 32 insertions, 11 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index e176bd3936da..cb69f717799f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1905,19 +1905,25 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
#endif
/* is kswapd sleeping prematurely? */
-static int sleeping_prematurely(int order, long remaining)
+static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
{
- struct zone *zone;
+ int i;
/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
if (remaining)
return 1;
/* If after HZ/10, a zone is below the high mark, it's premature */
- for_each_populated_zone(zone)
+ for (i = 0; i < pgdat->nr_zones; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
0, 0))
return 1;
+ }
return 0;
}
@@ -1979,6 +1985,7 @@ loop_again:
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
unsigned long lru_pages = 0;
+ int has_under_min_watermark_zone = 0;
/* The swap token gets in the way of swapout... */
if (!priority)
@@ -2085,6 +2092,15 @@ loop_again:
if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
sc.may_writepage = 1;
+
+ /*
+ * We are still under min water mark. it mean we have
+ * GFP_ATOMIC allocation failure risk. Hurry up!
+ */
+ if (!zone_watermark_ok(zone, order, min_wmark_pages(zone),
+ end_zone, 0))
+ has_under_min_watermark_zone = 1;
+
}
if (all_zones_ok)
break; /* kswapd: all done */
@@ -2092,8 +2108,12 @@ loop_again:
* OK, kswapd is getting into trouble. Take a nap, then take
* another pass across the zones.
*/
- if (total_scanned && priority < DEF_PRIORITY - 2)
- congestion_wait(BLK_RW_ASYNC, HZ/10);
+ if (total_scanned && (priority < DEF_PRIORITY - 2)) {
+ if (has_under_min_watermark_zone)
+ count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
+ else
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+ }
/*
* We do this so kswapd doesn't build up large priorities for
@@ -2207,7 +2227,7 @@ static int kswapd(void *p)
long remaining = 0;
/* Try to sleep for a short interval */
- if (!sleeping_prematurely(order, remaining)) {
+ 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);
@@ -2218,13 +2238,13 @@ static int kswapd(void *p)
* premature sleep. If not, then go fully
* to sleep until explicitly woken up
*/
- if (!sleeping_prematurely(order, remaining))
+ if (!sleeping_prematurely(pgdat, order, remaining))
schedule();
else {
if (remaining)
- count_vm_event(KSWAPD_PREMATURE_FAST);
+ count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
else
- count_vm_event(KSWAPD_PREMATURE_SLOW);
+ count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
}
}
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 63ab71455c5b..6051fbab67ba 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -683,8 +683,9 @@ static const char * const vmstat_text[] = {
"slabs_scanned",
"kswapd_steal",
"kswapd_inodesteal",
- "kswapd_slept_prematurely_fast",
- "kswapd_slept_prematurely_slow",
+ "kswapd_low_wmark_hit_quickly",
+ "kswapd_high_wmark_hit_quickly",
+ "kswapd_skip_congestion_wait",
"pageoutrun",
"allocstall",