On Fri, Apr 02, 2021 at 09:45:12AM +0200, Greg KH wrote:
> Why is the buffer alignment considered a "waste" here? If that change
> is in Linus's tree and newer kernels (it showed up in 5.4 which was
> released quite a while ago), where are the people complaining about it
> there?
>
> I think backporting 59bb47985c1d ("mm, sl[aou]b: guarantee natural
> alignment for kmalloc(power-of-two)") seems like the correct thing to do
> here to bring things into alignment (pun intended) with newer kernels.
It's only a waste for slabs which need things like redzones (eg we could
get 7 512-byte allocations out of a 4kB page with a 64 byte redzone
and no alignment ; with alignment we can only get four). Since slub
can enable/disable redzones on a per-slab basis, and redzones aren't
terribly interesting now that we have kasan/kfence, nobody really cares.
