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

[Yosry Ahmed]

On Mon, Jan 22, 2024 at 12:49 PM Yosry Ahmed <yosryahmed at google.com> wrote:
>
> On Sun, Jan 21, 2024 at 11:42 PM Christoph Hellwig <hch at infradead.org> wrote:
> >
> > On Tue, Jan 16, 2024 at 12:19:39PM -0800, Yosry Ahmed wrote:
> > > Well, better compression ratios for one :)
> > >
> > > I think a long time ago there were complaints that zsmalloc had higher
> > > latency than zbud/z3fold, but since then a lot of things have changed
> > > (including nice compaction optimization from Sergey, and compaction
> > > was one of the main factors AFAICT). Also, recent experiments that
> > > Chris Li conducted showed that (at least in our setup), the
> > > decompression is only a small part of the fault latency with zswap
> > > (i.e. not the main factor) -- so I am not sure if it actually matters
> > > in practice.
> > >
> > > That said, I have not conducted any experiments personally with z3fold
> > > or zbud, which is why I proposed the conservative approach of marking
> > > as deprecated first. However, if others believe this is unnecessary I
> > > am fine with removal as well. Whatever we agree on is fine by me.
> >
> > In general deprecated is for code that has active (intentional) users
> > and/or would break setups.  I does sound to me like that is not the
> > case here, but others might understand this better.
>
> I generally agree. So far we have no knowledge of active users, and if
> there are some, I expect most of them to be able to switch to zsmalloc
> with no problems. That being said, I was trying to take the
> conservative approach. If others agree I can send a removal patch
> instead.

Andrew, do you have an opinion here?

We are not sure that there are active users for z3fold. It seems like
we have all sorts of opinions here from "don't deprecate" to "remove
directly, no need to deprecate first".