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mm/mglru: use explicit tier range in read_ctrl_pos()

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read_ctrl_pos() encodes the tier range in a single "tier" parameter via
"tier % MAX_NR_TIERS" as the start and "min(tier, MAX_NR_TIERS-1)" as the
end.  This is hard to follow, maintain, or extend.  Tier values 0..3
select a single tier, while tier == MAX_NR_TIERS selects the full range.

Replace it with explicit (tier_min, tier_max) parameters using a closed
[tier_min, tier_max] interval, and add LRU_TIER_MIN and LRU_TIER_MAX for
the tier bounds.  The call sites now become self-documenting:

  - get_tier_idx:   (LRU_TIER_MIN, LRU_TIER_MIN) for the first tier,
                    (tier, tier) for each subsequent tier
  - get_type_to_scan: (LRU_TIER_MIN, LRU_TIER_MAX) for the full range

No functional change.

Link: https://lore.kernel.org/20260906-mglru-flags-cleanup-v6-5-9aacbd77d4ca@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Baoquan He <baoquan.he@linux.dev>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Ridong Chen <ridong.chen@linux.dev>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lian Wang <lianux.mm@gmail.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
This commit is contained in:
Kairui Song 2026-09-06 00:51:10 +08:00 committed by Andrew Morton
parent d896c1a837
commit c1d0e79932
2 changed files with 12 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/mmzone.h
View File

@ -495,6 +495,8 @@ enum lruvec_flags {
* folio->flags, masked by LRU_REFS_MASK.
*/
#define MAX_NR_TIERS 4U
#define LRU_TIER_MIN 0U
#define LRU_TIER_MAX (MAX_NR_TIERS - 1)
#ifndef __GENERATING_BOUNDS_H

18
mm/vmscan.c
View File

@ -3223,8 +3223,8 @@ struct ctrl_pos {
int gain;
};
static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
struct ctrl_pos *pos)
static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier_min,
int tier_max, int gain, struct ctrl_pos *pos)
{
int i;
struct lru_gen_folio *lrugen = &lruvec->lrugen;
@ -3233,7 +3233,7 @@ static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
pos->gain = gain;
pos->refaulted = pos->total = 0;
for (i = tier % MAX_NR_TIERS; i <= min(tier, MAX_NR_TIERS - 1); i++) {
for (i = tier_min; i <= tier_max; i++) {
pos->refaulted += lrugen->avg_refaulted[type][i] +
atomic_long_read(&lrugen->refaulted[hist][type][i]);
pos->total += lrugen->avg_total[type][i] +
@ -4879,9 +4879,9 @@ static int get_tier_idx(struct lruvec *lruvec, int type)
* This value is chosen because any other tier would have at least twice
* as many refaults as the first tier.
*/
read_ctrl_pos(lruvec, type, 0, 2, &sp);
for (tier = 1; tier < MAX_NR_TIERS; tier++) {
read_ctrl_pos(lruvec, type, tier, 3, &pv);
read_ctrl_pos(lruvec, type, LRU_TIER_MIN, LRU_TIER_MIN, 2, &sp);
for (tier = LRU_TIER_MIN + 1; tier <= LRU_TIER_MAX; tier++) {
read_ctrl_pos(lruvec, type, tier, tier, 3, &pv);
if (!positive_ctrl_err(&sp, &pv))
break;
}
@ -4902,8 +4902,10 @@ static int get_type_to_scan(struct lruvec *lruvec, int swappiness)
* Compare the sum of all tiers of anon with that of file to determine
* which type to scan.
*/
read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp);
read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv);
read_ctrl_pos(lruvec, LRU_GEN_ANON, LRU_TIER_MIN, LRU_TIER_MAX,
swappiness, &sp);
read_ctrl_pos(lruvec, LRU_GEN_FILE, LRU_TIER_MIN, LRU_TIER_MAX,
MAX_SWAPPINESS - swappiness, &pv);
return positive_ctrl_err(&sp, &pv);
}