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mm: add max swappiness arg to lru_gen for anonymous memory only

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The MGLRU already supports reclaiming only from anonymous memory via the
/sys/kernel/debug/lru_gen interface.  Now, memory.reclaim also supports
the swappiness=max parameter to enable reclaiming solely from anonymous
memory.  To unify the semantics of proactive reclaiming from anonymous
folios, the max parameter is introduced.

[hezhongkun.hzk@bytedance.com: use strcmp instead of strncmp, if swappiness is not set, use the default value]
  Link: https://lkml.kernel.org/r/20250507071057.3184240-1-hezhongkun.hzk@bytedance.com
[akpm@linux-foundation.org: tweak coding style]
Link: https://lkml.kernel.org/r/65181f7745d657d664d833c26d8a94cae40538b9.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zhongkun He
2025-04-21 17:13:30 +08:00
committed by Andrew Morton
parent aded729f64
commit b40599930f
2 changed files with 18 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
Documentation/admin-guide/mm/multigen_lru.rst
View File

@@ -151,8 +151,9 @@ generations less than or equal to ``min_gen_nr``.
``min_gen_nr`` should be less than ``max_gen_nr-1``, since
``max_gen_nr`` and ``max_gen_nr-1`` are not fully aged (equivalent to
the active list) and therefore cannot be evicted. ``swappiness``
overrides the default value in ``/proc/sys/vm/swappiness``.
``nr_to_reclaim`` limits the number of pages to evict.
overrides the default value in ``/proc/sys/vm/swappiness`` and the valid
range is [0-200, max], with max being exclusively used for the reclamation
of anonymous memory. ``nr_to_reclaim`` limits the number of pages to evict.
A typical use case is that a job scheduler runs this command before it
tries to land a new job on a server. If it fails to materialize enough

19
mm/vmscan.c
View File

@@ -5588,24 +5588,35 @@ static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
while ((cur = strsep(&next, ",;\n"))) {
int n;
int end;
char cmd;
char cmd, swap_string[5];
unsigned int memcg_id;
unsigned int nid;
unsigned long seq;
unsigned int swappiness = -1;
unsigned int swappiness;
unsigned long opt = -1;
cur = skip_spaces(cur);
if (!*cur)
continue;
n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid,
&seq, &end, &swappiness, &end, &opt, &end);
n = sscanf(cur, "%c %u %u %lu %n %4s %n %lu %n", &cmd, &memcg_id, &nid,
&seq, &end, swap_string, &end, &opt, &end);
if (n < 4 || cur[end]) {
err = -EINVAL;
break;
}
if (n == 4) {
swappiness = -1;
} else if (!strcmp("max", swap_string)) {
/* set by userspace for anonymous memory only */
swappiness = SWAPPINESS_ANON_ONLY;
} else {
err = kstrtouint(swap_string, 0, &swappiness);
if (err)
break;
}
err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt);
if (err)
break;