Re: [PATCH 1/1] mm/thp: clear deferred split shrinker bits when queues drain

[Andrew Morton]

On Tue,  2 Jun 2026 12:34:53 +0800 Lance Yang <lance.yang@xxxxxxxxx> wrote:

> From: Lance Yang <lance.yang@xxxxxxxxx>
> 
> deferred_split_count() returns the raw list_lru count. When the per-memcg,
> per-node list is empty, that count is 0.
> 
> That skips scanning, but it does not tell memcg reclaim that the shrinker
> is empty. shrink_slab_memcg() only clears the memcg shrinker bit when the
> count callback reports SHRINK_EMPTY.
> 
> Return SHRINK_EMPTY for an empty deferred split list, so the bit can be
> cleared once the queue has drained.
> 
> Signed-off-by: Lance Yang <lance.yang@xxxxxxxxx>
> ---
>  mm/huge_memory.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 72f6caf0fec6..62d598290c3b 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -4397,7 +4397,10 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped)
>  static unsigned long deferred_split_count(struct shrinker *shrink,
>  		struct shrink_control *sc)
>  {
> -	return list_lru_shrink_count(&deferred_split_lru, sc);
> +	unsigned long count;
> +
> +	count = list_lru_shrink_count(&deferred_split_lru, sc);
> +	return count ?: SHRINK_EMPTY;
>  }
>  
>  static bool thp_underused(struct folio *folio)

Should this be handled as a fix against hannes's "mm: switch deferred
split shrinker to list_lru"?