From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
The test case of [1] leads to system hang which caused by a local
watchdog thread starved over 20s on a 5.5GB RAM ANDROID15(v6.6)
system. This commit solve the issue by have the reclaimer be throttled
and increase min_seq if both page types reach MIN_NR_GENS, which may
introduce a livelock of switching type with holding lruvec->lru_lock.
[1]
launch below script 8 times simutanously which allocates 1GB virtual
memory and access it from user space by each thread.
$ costmem -c1024000 -b12800 -o0 &
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
mm/vmscan.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index cfa839284b92..83e450d0ce3c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4384,11 +4384,23 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
int remaining = MAX_LRU_BATCH;
struct lru_gen_folio *lrugen = &lruvec->lrugen;
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
VM_WARN_ON_ONCE(!list_empty(list));
- if (get_nr_gens(lruvec, type) == MIN_NR_GENS)
- return 0;
+ if (get_nr_gens(lruvec, type) == MIN_NR_GENS) {
+ /*
+ * throttle for a while and then increase the min_seq since
+ * both page types reach the limit.
+ */
+ if (get_nr_gens(lruvec, !type) == MIN_NR_GENS) {
+ spin_unlock_irq(&lruvec->lru_lock);
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
+ spin_lock_irq(&lruvec->lru_lock);
+ try_to_inc_min_seq(lruvec, get_swappiness(lruvec, sc));
+ } else
+ return 0;
+ }
gen = lru_gen_from_seq(lrugen->min_seq[type]);
--
2.25.1
