mm: vmscan: add more comments about cache_trim_mode

Add more comments for cache_trim_mode, and the annotations provided by
Johannes Weiner in [1].

Link: https://lore.kernel.org/all/20250314141833.GA1316033@cmpxchg.org/
Link: https://lkml.kernel.org/r/4baad87ba637f1e6f666e9b99b3fdcb7ab39171b.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
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 495889f621b5598d48a3f80213c19fee3b3f820d..ca786575b6c2e67f33c6d72a7be7253ae85a3d8e 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2536,7 +2536,8 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 
        /*
         * If there is enough inactive page cache, we do not reclaim
-        * anything from the anonymous working right now.
+        * anything from the anonymous working right now to make sure
+         * a streaming file access pattern doesn't cause swapping.
         */
        if (sc->cache_trim_mode) {
                scan_balance = SCAN_FILE;