The patch titled
Subject: mm: throttle and inc min_seq when both page types reach MIN_NR_GENS
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-throttle-and-inc-min_seq-when-both-page-types-reach-min_nr_gens.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-throttle-and-inc-min_seq-when-both-page-types-reach-min_nr_gens.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Subject: mm: throttle and inc min_seq when both page types reach MIN_NR_GENS
Date: Wed, 9 Oct 2024 15:49:53 +0800
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 &
Link: https://lkml.kernel.org/r/20241009074953.608591-1-zhaoyang.huang@xxxxxxxxxx
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
--- a/mm/vmscan.c~mm-throttle-and-inc-min_seq-when-both-page-types-reach-min_nr_gens
+++ a/mm/vmscan.c
@@ -4387,11 +4387,23 @@ static int scan_folios(struct lruvec *lr
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]);
_
Patches currently in -mm which might be from zhaoyang.huang@xxxxxxxxxx are
mm-throttle-and-inc-min_seq-when-both-page-types-reach-min_nr_gens.patch
mm-migrate-lru_refs_mask-bits-in-folio_migrate_flags.patch
mm-optimization-on-page-allocation-when-cma-enabled.patch
