mm: vmscan: correct nr_requested tracing in scan_folios

When enabling vmscan tracing, it is observed that nr_requested is always
4096, which is confusing.

        mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ...
        mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ...
        mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ...
        mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ...
        mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ...
        mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ...
        mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ...

This is because it prints MAX_LRU_BATCH, which is meaningless as it's a
constant.  To fix this, modify it to print capped valued.

Link: https://lkml.kernel.org/r/20251204122355.1822919-1-chenridong@huaweicloud.com
Fixes: 8c2214fc9a47 ("mm: multi-gen LRU: reuse some legacy trace events")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Jaewon Kim <jaewon31.kim@samsung.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Lu Jialin <lujialin4@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3b85652a42b960d574e269348dae4414882514ff..7fcc0120a72bd53b7252fd7afdee5bb4d37f1c6b 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4541,7 +4541,8 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
        int scanned = 0;
        int isolated = 0;
        int skipped = 0;
-       int remaining = min(nr_to_scan, MAX_LRU_BATCH);
+       int scan_batch = min(nr_to_scan, MAX_LRU_BATCH);
+       int remaining = scan_batch;
        struct lru_gen_folio *lrugen = &lruvec->lrugen;
        struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 
@@ -4601,7 +4602,7 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
        count_memcg_events(memcg, item, isolated);
        count_memcg_events(memcg, PGREFILL, sorted);
        __count_vm_events(PGSCAN_ANON + type, isolated);
-       trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
+       trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, scan_batch,
                                scanned, skipped, isolated,
                                type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
        if (type == LRU_GEN_FILE)