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

Jason A. Donenfeld
2024-06-14T19:33:58Z

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-MI@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