linux-kernel - Re: oom-killer not invoked on systems with multiple memory-tiers

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Message-ID: <20251028072736.10455-1-akinobu.mita@gmail.com>
Date: Tue, 28 Oct 2025 16:27:36 +0900
From: Akinobu Mita <akinobu.mita@...il.com>
To: akinobu.mita@...il.com
Cc: linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	akpm@...ux-foundation.org,
	axelrasmussen@...gle.com,
	yuanchu@...gle.com,
	weixugc@...gle.com,
	hannes@...xchg.org,
	david@...hat.com,
	mhocko@...nel.org,
	zhengqi.arch@...edance.com,
	shakeel.butt@...ux.dev,
	lorenzo.stoakes@...cle.com
Subject: Re: oom-killer not invoked on systems with multiple memory-tiers

lru_gen_age_node() checks the reclaimability of a node using
lruvec_is_reclaimable() when min_ttl_ms is non-zero, but if min_ttl_ms
is zero, it unconditionally determines that the node is reclaimable.

I think we should still call lruvec_is_reclaimable() to check
reclaimability even if min_ttl_ms is zero.
Otherwise, we'll miss the opportunity to trigger an OOM kill in
lru_gen_age_node(), which will cause the problem I reported.

https://lore.kernel.org/linux-mm/20251022135735.246203-1-akinobu.mita@gmail.com/

The attached patch made the changes mentioned above and worked around
the problem.

---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c922bad2b8fd..e1a88ed4e0b0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4148,7 +4148,7 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
 {
 	struct mem_cgroup *memcg;
 	unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);
-	bool reclaimable = !min_ttl;
+	bool reclaimable = false;

 	VM_WARN_ON_ONCE(!current_is_kswapd());

-- 
2.43.0