Re: [PATCH 00/14] replace call_rcu by kfree_rcu for simple kmem_cache_free callback

[Jason A. Donenfeld]

On Fri, Jun 14, 2024 at 02:35:33PM +0200, Uladzislau Rezki wrote:
> +     /* Should a destroy process be deferred? */
> +     if (s->flags & SLAB_DEFER_DESTROY) {
> +             list_move_tail(&s->list, &slab_caches_defer_destroy);
> +             schedule_delayed_work(&slab_caches_defer_destroy_work, HZ);
> +             goto out_unlock;
> +     }

Wouldn't it be smoother to have the actual kmem_cache_free() function
check to see if it's been marked for destruction and the refcount is
zero, rather than polling every one second? I mentioned this approach
in: https://lore.kernel.org/all/zmo9-ygraicj5...@zx2c4.com/ -

    I wonder if the right fix to this would be adding a `should_destroy`
    boolean to kmem_cache, which kmem_cache_destroy() sets to true. And
    then right after it checks `if (number_of_allocations == 0)
    actually_destroy()`, and likewise on each kmem_cache_free(), it
    could check `if (should_destroy && number_of_allocations == 0)
    actually_destroy()`. 

Jason