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

[Lance Yang <lance.yang@linux.dev>]

Sorry, I missed Johannes in Cc ...

On 2026/6/2 12:34, Lance Yang wrote:
> From: Lance Yang <lance.yang@linux.dev>
> 
> 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@linux.dev>
> ---
>   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)