Re: [RFC PATCH V3 6/7] mm/slab: save memory by allocating slabobj_ext array from leftover

[Andrey Ryabinin]

On 10/27/25 1:28 PM, Harry Yoo wrote:

>  
> +#ifdef CONFIG_SLAB_OBJ_EXT
> +
> +/*
> + * Check if memory cgroup or memory allocation profiling is enabled.
> + * If enabled, SLUB tries to reduce memory overhead of accounting
> + * slab objects. If neither is enabled when this function is called,
> + * the optimization is simply skipped to avoid affecting caches that do not
> + * need slabobj_ext metadata.
> + *
> + * However, this may disable optimization when memory cgroup or memory
> + * allocation profiling is used, but slabs are created too early
> + * even before those subsystems are initialized.
> + */
> +static inline bool need_slab_obj_exts(struct kmem_cache *s)
> +{
> +	if (!mem_cgroup_disabled() && (s->flags & SLAB_ACCOUNT))

Shouldn't this be !memcg_kmem_online() check?
In case of disabled kmem accounting via 'cgroup.memory=nokmem'

> +		return true;
> +
> +	if (mem_alloc_profiling_enabled())
> +		return true;
> +
> +	return false;
> +}
> +