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

Uladzislau Rezki
2024-06-17T13:51:02Z

On Fri, Jun 14, 2024 at 09:33:45PM +0200, Jason A. Donenfeld wrote:
> 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()`.
>
I do not find pooling as bad way we can go with. But your proposal
sounds reasonable to me also. We can combine both "prototypes" to
one and offer.

Can you post a prototype here?

Thanks!

--
Uladzislau Rezki