From: lyugaofei This partially restores the reclaim behavior introduced in Yu Zhao's initial MGLRU commit, ac35a4902370 ("mm: multi-gen LRU: minimal implementation"): /* * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1) * of the total number of pages for each generation. A reasonable range * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The * aging cares about the upper bound of hot pages, while the eviction * cares about the lower bound of cold pages. */ if (young * MIN_NR_GENS > total) return true; if (old * (MIN_NR_GENS + 2) < total) return true; But with a stricter condition: the youngest gen must have at least four times as many folios as the oldest. This helps keep folios of the preferred type distributed across the reclaimable gens. Signed-off-by: lyugaofei Co-developed-by: Barry Song (Xiaomi) Signed-off-by: Barry Song (Xiaomi) --- mm/vmscan.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 4f3a375de86e..9aac4febc206 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4963,9 +4963,37 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, return scanned; } +static bool lru_gen_imbalanced(struct lruvec *lruvec, int type, + unsigned long max_seq, unsigned long min_seq, + int swappiness) +{ + struct lru_gen_folio *lrugen = &lruvec->lrugen; + unsigned long young = 0, old = 0, seq; + + if (swappiness == MIN_SWAPPINESS || swappiness > MAX_SWAPPINESS) + return false; + + for (seq = min_seq; seq <= max_seq; seq++) { + int gen = lru_gen_from_seq(seq); + unsigned long size = 0; + int zone; + + gen = lru_gen_from_seq(seq); + for (zone = 0; zone < MAX_NR_ZONES; zone++) + size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); + + if (seq + MIN_NR_GENS > max_seq) + young += size; + else + old += size; + } + return young > old * 4; +} + static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, struct scan_control *sc, int swappiness) { + int type = get_type_to_scan(lruvec, swappiness); DEFINE_MIN_SEQ(lruvec); /* have to run aging, since eviction is not possible anymore */ @@ -4977,7 +5005,11 @@ static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, return false; /* better to run aging even though eviction is still possible */ - return evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq; + if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq) + return true; + + /* Run aging if the preferred type is severely imbalanced across gens */ + return lru_gen_imbalanced(lruvec, type, max_seq, min_seq[type], swappiness); } static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, -- 2.39.3 (Apple Git-146)