The patch titled
Subject: mm: multi-gen LRU: avoid futile retries
has been added to the -mm mm-unstable branch. Its filename is
mm-multi-gen-lru-avoid-futile-retries.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-multi-gen-lru-avoid-futile-retries.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yu Zhao <yuzhao@xxxxxxxxxx>
Subject: mm: multi-gen LRU: avoid futile retries
Date: Mon, 13 Feb 2023 00:53:22 -0700
Recall that the per-node memcg LRU has two generations and they alternate
when the last memcg (of a given node) is moved from one to the other.
Each generation is also sharded into multiple bins to improve scalability.
A reclaimer starts with a random bin (in the old generation) and, if it
fails, it will retry, i.e., to try the rest of the bins.
If a reclaimer fails with the last memcg, it should move this memcg to the
young generation first, which causes the generations to alternate, and
then retry. Otherwise, the retries will be futile because all other bins
are empty.
Link: https://lkml.kernel.org/r/20230213075322.1416966-1-yuzhao@xxxxxxxxxx
Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Reported-by: T.J. Mercier <tjmercier@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/vmscan.c~mm-multi-gen-lru-avoid-futile-retries
+++ a/mm/vmscan.c
@@ -5356,18 +5356,20 @@ static int shrink_one(struct lruvec *lru
static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
{
+ int op;
int gen;
int bin;
int first_bin;
struct lruvec *lruvec;
struct lru_gen_folio *lrugen;
+ struct mem_cgroup *memcg;
const struct hlist_nulls_node *pos;
- int op = 0;
- struct mem_cgroup *memcg = NULL;
unsigned long nr_to_reclaim = get_nr_to_reclaim(sc);
bin = first_bin = get_random_u32_below(MEMCG_NR_BINS);
restart:
+ op = 0;
+ memcg = NULL;
gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq));
rcu_read_lock();
@@ -5391,14 +5393,22 @@ restart:
op = shrink_one(lruvec, sc);
- if (sc->nr_reclaimed >= nr_to_reclaim)
- goto success;
-
rcu_read_lock();
+
+ if (sc->nr_reclaimed >= nr_to_reclaim)
+ break;
}
rcu_read_unlock();
+ if (op)
+ lru_gen_rotate_memcg(lruvec, op);
+
+ mem_cgroup_put(memcg);
+
+ if (sc->nr_reclaimed >= nr_to_reclaim)
+ return;
+
/* restart if raced with lru_gen_rotate_memcg() */
if (gen != get_nulls_value(pos))
goto restart;
@@ -5407,11 +5417,6 @@ restart:
bin = get_memcg_bin(bin + 1);
if (bin != first_bin)
goto restart;
-success:
- if (op)
- lru_gen_rotate_memcg(lruvec, op);
-
- mem_cgroup_put(memcg);
}
static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
_
Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are
mm-multi-gen-lru-avoid-futile-retries.patch
