On Mon, Jan 22, 2024 at 12:49 PM Yosry Ahmed [off-list ref] wrote:

On Sun, Jan 21, 2024 at 11:42 PM Christoph Hellwig [off-list ref] wrote:

quoted

On Tue, Jan 16, 2024 at 12:19:39PM -0800, Yosry Ahmed wrote:

quoted

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".