Re: [PATCH v7 1/6] list_lru: allows explicit memcg and NUMA node selection

[Johannes Weiner <hannes@cmpxchg.org>]

On Mon, Nov 27, 2023 at 03:45:55PM -0800, Nhat Pham wrote:
> The interface of list_lru is based on the assumption that the list node
> and the data it represents belong to the same allocated on the correct
> node/memcg. While this assumption is valid for existing slab objects LRU
> such as dentries and inodes, it is undocumented, and rather inflexible
> for certain potential list_lru users (such as the upcoming zswap
> shrinker and the THP shrinker). It has caused us a lot of issues during
> our development.
> 
> This patch changes list_lru interface so that the caller must explicitly
> specify numa node and memcg when adding and removing objects. The old
> list_lru_add() and list_lru_del() are renamed to list_lru_add_obj() and
> list_lru_del_obj(), respectively.
> 
> It also extends the list_lru API with a new function, list_lru_putback,
> which undoes a previous list_lru_isolate call. Unlike list_lru_add, it
> does not increment the LRU node count (as list_lru_isolate does not
> decrement the node count). list_lru_putback also allows for explicit
> memcg and NUMA node selection.
> 
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Nhat Pham <nphamcs@gmail.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>