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authorGregory Price <gourry@gourry.net>2024-10-25 10:17:24 -0400
committerAndrew Morton <akpm@linux-foundation.org>2024-10-31 20:27:04 -0700
commit35e41024c4c2b02ef8207f61b9004f6956cf037b (patch)
tree269f2335e0b074b23bbfc4a27f6db8fe1e5b567e
parent85d16bceaf5d8112c9ffcfedd2f1bb9d0a1c1578 (diff)
vmscan,migrate: fix page count imbalance on node stats when demoting pages
When numa balancing is enabled with demotion, vmscan will call migrate_pages when shrinking LRUs. migrate_pages will decrement the the node's isolated page count, leading to an imbalanced count when invoked from (MG)LRU code. The result is dmesg output like such: $ cat /proc/sys/vm/stat_refresh [77383.088417] vmstat_refresh: nr_isolated_anon -103212 [77383.088417] vmstat_refresh: nr_isolated_file -899642 This negative value may impact compaction and reclaim throttling. The following path produces the decrement: shrink_folio_list demote_folio_list migrate_pages migrate_pages_batch migrate_folio_move migrate_folio_done mod_node_page_state(-ve) <- decrement This path happens for SUCCESSFUL migrations, not failures. Typically callers to migrate_pages are required to handle putback/accounting for failures, but this is already handled in the shrink code. When accounting for migrations, instead do not decrement the count when the migration reason is MR_DEMOTION. As of v6.11, this demotion logic is the only source of MR_DEMOTION. Link: https://lkml.kernel.org/r/20241025141724.17927-1-gourry@gourry.net Fixes: 26aa2d199d6f ("mm/migrate: demote pages during reclaim") Signed-off-by: Gregory Price <gourry@gourry.net> Reviewed-by: Yang Shi <shy828301@gmail.com> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net> Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Wei Xu <weixugc@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--mm/migrate.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 7e520562d421..fab84a776088 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1178,7 +1178,7 @@ static void migrate_folio_done(struct folio *src,
* not accounted to NR_ISOLATED_*. They can be recognized
* as __folio_test_movable
*/
- if (likely(!__folio_test_movable(src)))
+ if (likely(!__folio_test_movable(src)) && reason != MR_DEMOTION)
mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
folio_is_file_lru(src), -folio_nr_pages(src));