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-rw-r--r--mm/vmscan.c49
1 files changed, 33 insertions, 16 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 999ef0b9399a..5b1a79c8f0cb 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -697,6 +697,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
enum ttu_flags ttu_flags,
unsigned long *ret_nr_unqueued_dirty,
unsigned long *ret_nr_writeback,
+ unsigned long *ret_nr_immediate,
bool force_reclaim)
{
LIST_HEAD(ret_pages);
@@ -707,6 +708,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
unsigned long nr_congested = 0;
unsigned long nr_reclaimed = 0;
unsigned long nr_writeback = 0;
+ unsigned long nr_immediate = 0;
cond_resched();
@@ -773,8 +775,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
* IO can complete. Waiting on the page itself risks an
* indefinite stall if it is impossible to writeback the
* page due to IO error or disconnected storage so instead
- * block for HZ/10 or until some IO completes then clear the
- * ZONE_WRITEBACK flag to recheck if the condition exists.
+ * note that the LRU is being scanned too quickly and the
+ * caller can stall after page list has been processed.
*
* 2) Global reclaim encounters a page, memcg encounters a
* page that is not marked for immediate reclaim or
@@ -804,10 +806,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
if (current_is_kswapd() &&
PageReclaim(page) &&
zone_is_reclaim_writeback(zone)) {
- unlock_page(page);
- congestion_wait(BLK_RW_ASYNC, HZ/10);
- zone_clear_flag(zone, ZONE_WRITEBACK);
- goto keep;
+ nr_immediate++;
+ goto keep_locked;
/* Case 2 above */
} else if (global_reclaim(sc) ||
@@ -1033,6 +1033,7 @@ keep:
mem_cgroup_uncharge_end();
*ret_nr_unqueued_dirty += nr_unqueued_dirty;
*ret_nr_writeback += nr_writeback;
+ *ret_nr_immediate += nr_immediate;
return nr_reclaimed;
}
@@ -1044,7 +1045,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
.priority = DEF_PRIORITY,
.may_unmap = 1,
};
- unsigned long ret, dummy1, dummy2;
+ unsigned long ret, dummy1, dummy2, dummy3;
struct page *page, *next;
LIST_HEAD(clean_pages);
@@ -1057,7 +1058,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
ret = shrink_page_list(&clean_pages, zone, &sc,
TTU_UNMAP|TTU_IGNORE_ACCESS,
- &dummy1, &dummy2, true);
+ &dummy1, &dummy2, &dummy3, true);
list_splice(&clean_pages, page_list);
__mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
return ret;
@@ -1353,6 +1354,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
unsigned long nr_taken;
unsigned long nr_unqueued_dirty = 0;
unsigned long nr_writeback = 0;
+ unsigned long nr_immediate = 0;
isolate_mode_t isolate_mode = 0;
int file = is_file_lru(lru);
struct zone *zone = lruvec_zone(lruvec);
@@ -1394,7 +1396,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
return 0;
nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
- &nr_unqueued_dirty, &nr_writeback, false);
+ &nr_unqueued_dirty, &nr_writeback, &nr_immediate,
+ false);
spin_lock_irq(&zone->lru_lock);
@@ -1447,14 +1450,28 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
}
/*
- * Similarly, if many dirty pages are encountered that are not
- * currently being written then flag that kswapd should start
- * writing back pages and stall to give a chance for flushers
- * to catch up.
+ * memcg will stall in page writeback so only consider forcibly
+ * stalling for global reclaim
*/
- if (global_reclaim(sc) && nr_unqueued_dirty == nr_taken) {
- congestion_wait(BLK_RW_ASYNC, HZ/10);
- zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
+ if (global_reclaim(sc)) {
+ /*
+ * If dirty pages are scanned that are not queued for IO, it
+ * implies that flushers are not keeping up. In this case, flag
+ * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing
+ * pages from reclaim context. It will forcibly stall in the
+ * next check.
+ */
+ if (nr_unqueued_dirty == nr_taken)
+ zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
+
+ /*
+ * In addition, if kswapd scans pages marked marked for
+ * immediate reclaim and under writeback (nr_immediate), it
+ * implies that pages are cycling through the LRU faster than
+ * they are written so also forcibly stall.
+ */
+ if (nr_unqueued_dirty == nr_taken || nr_immediate)
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
}
trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,