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mm/damon: adjust isolated pages stat for DAMOS_MIGRATE_{HOT,COLD}

PATCH Applied SJ Park 1 participant 1 message Jul 28

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SJ Park

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PATCH 1/1 mm/damon: adjust isolated pages stat for DAMOS_MIGRATE_{HOT,COLD}

Callers of migrate_pages() should adjust NR_MIGRATED_{ANON,FILE} for isolations and putback of the folios. That for migration succeeded folios is done by migrate_pages(), in migrate_folio_done(). That for MR_DEMOTION reason is an exception though.

DAMOS_MIGRATE_{HOT,COLD} call migrate_pages() but mistakenly not doing the stat adjustment. As a result, use of DAMOS_MIGRATE_{HOT,COLD} could corrupt the stat. It could confuse too_many_isolated(), make compaction and reclaim to behave in unexpected ways. The stat corruption can be reproduced and confirmed using DAMON user-space tool [1] on NUMA systems, like below.

    $ numactl --hardware
    available: 2 nodes (0-1)
    [...]
    $ sudo ./damo start --damos_action migrate_hot 1
    $ sudo cat /proc/sys/vm/stat_refresh
    $ sudo dmesg
    [...]
    [   80.215554] vmstat_refresh: nr_isolated_anon -5578
    [   80.216842] vmstat_refresh: nr_isolated_file -34400

This issue was discovered [2] by Sashiko.

[1] https://github.com/damonitor/damo
[2] https://lore.kernel.org/[email protected]

Fixes b51820ebea65 ("mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion")
Cc <[email protected]> # 6.11.x
Signed-off-by SJ Park <[email protected]>

---
Changes from RFC:
- RFC: https://lore.kernel.org/[email protected]
- Rebase to the latest mm-new.
- Drop RFC tag.

 mm/damon/ops-common.c | 4 ++++
 mm/damon/paddr.c      | 2 ++
 mm/damon/vaddr.c      | 3 ++-
 3 files changed, 8 insertions(+), 1 deletion(-)
mm/damon/ops-common.c +4 -0
index 0981a5e3af172..fbda70d8ea4d0 100644
@@ -374,6 +374,8 @@ static unsigned int damon_migrate_folio_list(struct list_head *folio_list,
 	while (!list_empty(folio_list)) {
 		folio = lru_to_folio(folio_list);
 		list_del(&folio->lru);
+		node_stat_sub_folio(folio, NR_ISOLATED_ANON +
+				folio_is_file_lru(folio));
 		folio_putback_lru(folio);
 	}
 

@@ -396,6 +398,8 @@ unsigned long damon_migrate_pages(struct list_head *folio_list, int target_nid)
 			struct folio *folio = lru_to_folio(folio_list);
 
 			list_del(&folio->lru);
+			node_stat_sub_folio(folio, NR_ISOLATED_ANON +
+					folio_is_file_lru(folio));
 			folio_putback_lru(folio);
 		}
 		return nr_migrated;
mm/damon/paddr.c +2 -0
index 5a6a78054784a..5c6c3a597fd0b 100644
@@ -346,6 +346,8 @@ static unsigned long damon_pa_migrate(struct damon_region *r,
 
 		if (!folio_isolate_lru(folio))
 			goto put_folio;
+		node_stat_add_folio(folio, NR_ISOLATED_ANON +
+				folio_is_file_lru(folio));
 		list_add(&folio->lru, &folio_list);
 put_folio:
 		addr += folio_size(folio);
mm/damon/vaddr.c +2 -1
index 4976775fe2762..0648400b2d65b 100644
@@ -627,7 +627,8 @@ static void damos_va_migrate_dests_add(struct folio *folio,
 isolate:
 	if (!folio_isolate_lru(folio))
 		return;
-
+	node_stat_add_folio(folio, NR_ISOLATED_ANON +
+			folio_is_file_lru(folio));
 	list_add(&folio->lru, &migration_lists[i]);
 }

base-commit: 53f9deb696041883ca3d03b33b565e4cd3ba54dd

Signature · 1 line
2.47.3