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89 lines
2.5 KiB
Diff
89 lines
2.5 KiB
Diff
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From cc67f962cc53f6e1dfa92eb85b7b26fe83a3c66f Mon Sep 17 00:00:00 2001
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From: Yu Zhao <yuzhao@google.com>
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Date: Mon, 13 Feb 2023 00:53:22 -0700
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Subject: [PATCH 29/29] mm: multi-gen LRU: avoid futile retries
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Recall that the per-node memcg LRU has two generations and they alternate
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when the last memcg (of a given node) is moved from one to the other.
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Each generation is also sharded into multiple bins to improve scalability.
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A reclaimer starts with a random bin (in the old generation) and, if it
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fails, it will retry, i.e., to try the rest of the bins.
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If a reclaimer fails with the last memcg, it should move this memcg to the
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young generation first, which causes the generations to alternate, and
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then retry. Otherwise, the retries will be futile because all other bins
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are empty.
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Link: https://lkml.kernel.org/r/20230213075322.1416966-1-yuzhao@google.com
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Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
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Signed-off-by: Yu Zhao <yuzhao@google.com>
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Reported-by: T.J. Mercier <tjmercier@google.com>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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---
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mm/vmscan.c | 25 +++++++++++++++----------
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1 file changed, 15 insertions(+), 10 deletions(-)
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--- a/mm/vmscan.c
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+++ b/mm/vmscan.c
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@@ -4934,18 +4934,20 @@ static int shrink_one(struct lruvec *lru
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static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
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{
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+ int op;
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int gen;
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int bin;
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int first_bin;
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struct lruvec *lruvec;
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struct lru_gen_page *lrugen;
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+ struct mem_cgroup *memcg;
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const struct hlist_nulls_node *pos;
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- int op = 0;
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- struct mem_cgroup *memcg = NULL;
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unsigned long nr_to_reclaim = get_nr_to_reclaim(sc);
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bin = first_bin = prandom_u32_max(MEMCG_NR_BINS);
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restart:
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+ op = 0;
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+ memcg = NULL;
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gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq));
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rcu_read_lock();
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@@ -4969,14 +4971,22 @@ restart:
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op = shrink_one(lruvec, sc);
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- if (sc->nr_reclaimed >= nr_to_reclaim)
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- goto success;
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-
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rcu_read_lock();
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+
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+ if (sc->nr_reclaimed >= nr_to_reclaim)
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+ break;
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}
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rcu_read_unlock();
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+ if (op)
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+ lru_gen_rotate_memcg(lruvec, op);
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+
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+ mem_cgroup_put(memcg);
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+
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+ if (sc->nr_reclaimed >= nr_to_reclaim)
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+ return;
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+
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/* restart if raced with lru_gen_rotate_memcg() */
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if (gen != get_nulls_value(pos))
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goto restart;
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@@ -4985,11 +4995,6 @@ restart:
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bin = get_memcg_bin(bin + 1);
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if (bin != first_bin)
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goto restart;
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-success:
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- if (op)
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- lru_gen_rotate_memcg(lruvec, op);
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-
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- mem_cgroup_put(memcg);
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}
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static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
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