Re: [PATCH v4 05/22] mm/slab: make caches with sheaves mergeable

Liam R. Howlett
2026-01-27T16:24:55Z

* Vlastimil Babka <vbabka@suse.cz> [260123 01:53]:
> Before enabling sheaves for all caches (with automatically determined
> capacity), their enablement should no longer prevent merging of caches.
> Limit this merge prevention only to caches that were created with a
> specific sheaf capacity, by adding the SLAB_NO_MERGE flag to them.
>
> Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
> mm/slab_common.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index ee245a880603..5c15a4ce5743 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -162,9 +162,6 @@ int slab_unmergeable(struct kmem_cache *s)
> return 1;
> #endif
>
> - if (s->cpu_sheaves)
> - return 1;
> -
> /*
> * We may have set a slab to be unmergeable during bootstrap.
> */
> @@ -189,9 +186,6 @@ static struct kmem_cache *find_mergeable(unsigned int size, slab_flags_t flags,
> if (IS_ENABLED(CONFIG_HARDENED_USERCOPY) && args->usersize)
> return NULL;
>
> - if (args->sheaf_capacity)
> - return NULL;
> -
> flags = kmem_cache_flags(flags, name);
>
> if (flags & SLAB_NEVER_MERGE)
> @@ -336,6 +330,13 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
> flags &= ~SLAB_DEBUG_FLAGS;
> #endif
>
> + /*
> + * Caches with specific capacity are special enough. It's simpler to
> + * make them unmergeable.
> + */
> + if (args->sheaf_capacity)
> + flags |= SLAB_NO_MERGE;
> +
> mutex_lock(&slab_mutex);
>
> err = kmem_cache_sanity_check(name, object_size);
>
> --
> 2.52.0
>
>