Re: [PATCH v3 1/4] mm: avoid unnecessary lru drain for wp_can_reuse_anon_folio()

[David Hildenbrand (Arm)]

On 7/2/26 01:59, Barry Song (Xiaomi) wrote:
> There is a case where `folio_ref_count(folio) == 3` and
> `!folio_test_swapcache(folio)`. In that case, both
> `folio_ref_count(folio) > 3` and
> `folio_ref_count(folio) > 1 + folio_test_swapcache(folio)` evaluate
> false, causing an unnecessary local LRU drain.
> 
> During an Ubuntu boot, I observed over 5,000 redundant local LRU
> drains. For a kernel build with a minimal configuration, I observed
> more than 20,000 redundant drains.
> 
> Fix this by checking against: `1 + in_swapcache + in_lrucache`
> instead of hardcoding `folio_ref_count(folio) > 3`.
> 
> Suggested-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> Reviewed-by: Kairui Song <kasong@xxxxxxxxxxx>
> Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Reviewed-by: Baoquan He <baoquan.he@xxxxxxxxx>
> Signed-off-by: Barry Song (Xiaomi) <baohua@xxxxxxxxxx>
> ---
The other folks should probably re-review this patch that changed quite a bit :)


Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David