Re: [PATCH v3 0/4] mm: clarify nofail memory allocation

[Linus Torvalds <torvalds@linux-foundation.org>]

On Thu, 22 Aug 2024 at 17:43, David Hildenbrand <david@redhat.com> wrote:
>
> So on the buddy level, that might mean that we limit it to a single
> page,

Actually, for many SLUB allocations, you probably do have to accept
the small orders - the slab caches are often two or four pages.

For example, a kmalloc(256) is an order-1 allocation on a buddy level
from a quick look at /proc/slabinfo.

So it's not necessarily only single pages. We do handle small orders.
But it gets exponentially harder, so it really is just the small
orders that work.

Looks like slub will use up to order-3. That smells like an off-by-one
to me (I thought we made 0-2 be the "cheap" orders, but maybe I'm just
wrong), but it probably is still acceptable.

             Linus