Re: [PATCH v3 17/21] slab: refill sheaves from all nodes

Harry Yoo
2026-01-22T07:03:03Z

On Fri, Jan 16, 2026 at 03:40:37PM +0100, Vlastimil Babka wrote:
> __refill_objects() currently only attempts to get partial slabs from the
> local node and then allocates new slab(s). Expand it to trying also
> other nodes while observing the remote node defrag ratio, similarly to
> get_any_partial().
>
> This will prevent allocating new slabs on a node while other nodes have
> many free slabs. It does mean sheaves will contain non-local objects in
> that case. Allocations that care about specific node will still be
> served appropriately, but might get a slowpath allocation.

Hmm one more question.

Given frees to remote nodes bypass sheaves layer anyway, isn't it
more reasonable to let refill_objects() fail sometimes instead of
allocating new local slabs and fall back to slowpath (based on defrag_ratio)?

> Like get_any_partial() we do observe cpuset_zone_allowed(), although we
> might be refilling a sheaf that will be then used from a different
> allocation context.
>
> We can also use the resulting refill_objects() in
> __kmem_cache_alloc_bulk() for non-debug caches. This means
> kmem_cache_alloc_bulk() will get better performance when sheaves are
> exhausted. kmem_cache_alloc_bulk() cannot indicate a preferred node so
> it's compatible with sheaves refill in preferring the local node.
> Its users also have gfp flags that allow spinning, so document that
> as a requirement.
>
> Reviewed-by: Suren Baghdasaryan <surenb@google.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---

--
Cheers,
Harry / Hyeonggon