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

[Nhat Pham]

On Sun, Jan 14, 2024 at 10:49 AM Yosry Ahmed <yosryahmed at google.com> wrote:
>
> On Fri, Jan 12, 2024 at 4:38 PM Nhat Pham <nphamcs at gmail.com> wrote:
> >
> > On Fri, Jan 12, 2024 at 3:37 PM Yosry Ahmed <yosryahmed at google.com> wrote:
> > >
> > > On Fri, Jan 12, 2024 at 11:42 AM Nhat Pham <nphamcs at gmail.com> wrote:
> > > >
> > > > On Fri, Jan 12, 2024 at 11:31 AM Yosry Ahmed <yosryahmed at 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.
> > > >
> > > > Johannes and I were chatting about this the other day. We might be
> > > > able to disable certain zsmalloc behavior in the case of !MMU, making
> > > > it available there too. Once that's happened, we can outright remove
> > > > z3fold and zbud, and have one allocator to rule them all? :)
> > >
> > > (Adding Sergey and Minchan for visibility)
> > >
> > > I didn't want to bring up the zsmalloc MMU dependency in this thread
> > > to reduce noise, but that's also what I had in mind. Sergey and I were
> > > also chatting about this the other day :)
> > >
> > > I thought deprecating z3fold is the low hanging fruit. Then, once we
> > > can sort out the MMU dependency in zsmalloc, we can go after zbud as
> > > well.
> >
> > Makes sense to me. Should we do the same thing to zbud? We probably
> > have even less of a case for it, no?
>
> Do you mean declare it as deprecated now? I initially thought that
> would only be appropriate to do after zsmalloc has no dependency on
> MMU, so that we can confidently say zbud has no practical use case.

Ah, I misread your email. My bad. Personally, I'd like to declare both
(zbud and z3fold) as deprecated. That said, no strong feelings here -
as long as (eventually) we move towards retiring both of them. So my
original ACK still holds.

Not entirely sure which should we remove first between zbud and z3fold
though. I was under the assumption that z3fold is slightly better, but
that could be my bias for shiny new things showing :)