Re: [RFC PATCH] mm: z3fold: rename CONFIG_Z3FOLD to CONFIG_Z3FOLD_DEPRECATED

[Yosry Ahmed <yosryahmed@google.com>]

On Mon, Jan 15, 2024 at 4:27 AM Vitaly Wool <vitaly.wool@konsulko.com> wrote:
>
> On Fri, Jan 12, 2024 at 8:31 PM Yosry Ahmed <yosryahmed@google.com> wrote:
> >
> > The z3fold compressed pages allocator is not widely used, most users use
> > zsmalloc. The only disadvantage of zsmalloc in comparison is the
> > dependency on MMU, and zbud is a more common option for !MMU as it was
> > the default zswap allocator for a long time.
> >
> > In hopes of having a single compressed pages allocator at some point,
> > and following in the footsteps of SLAB, deprecate z3fold. Rename the
> > user-visible option so that users with CONFIG_Z3FOLD=y get a new prompt
> > with explanation during make oldconfig. Remove CONFIG_Z3FOLD=y from
> > defconfigs.
>
> I believe that having a single compressed pages allocator is a false goal.

It's not a goal in itself for sure, but when most users use one
allocator that is mostly superior, it makes sense to try to deprecate
others.

>
> > Existing users, if any, should voice their objections. Otherwise, we can
> > remove z3fold in a few releases.
>
> At this point I NACK this patch. We're about to submit an allocator
> which is clearly better that z3fold and is faster that zsmalloc in
> most cases and that submission will mark z3fold as deprecated. But for
> now this move is premature.

I think unless there are current users of z3fold that cannot use
zsmalloc, the introduction of a new allocator should be irrelevant to
deprecating z3fold. Do you know of such users? Can you explain why
zsmalloc is not usable for them?