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

From: Yosry Ahmed <yosryahmed@google.com>
To: Nhat Pham <nphamcs@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Vitaly Wool <vitaly.wool@konsulko.com>,
	 Miaohe Lin <linmiaohe@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	 Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
	 Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	 Christophe Leroy <christophe.leroy@csgroup.eu>,
	"Aneesh Kumar K.V" <aneesh.kumar@kernel.org>,
	 "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	linux-mm@kvack.org, loongarch@lists.linux.dev,
	 linuxppc-dev@lists.ozlabs.org,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	 Minchan Kim <minchan@kernel.org>
Subject: Re: [RFC PATCH] mm: z3fold: rename CONFIG_Z3FOLD to CONFIG_Z3FOLD_DEPRECATED
Date: Fri, 12 Jan 2024 15:37:18 -0800	[thread overview]
Message-ID: <CAJD7tkYqKve5V4eJjbZE8kPZ=-5DU1Xh6jym8OfE1twQz-vbUA@mail.gmail.com> (raw)
In-Reply-To: <CAKEwX=PXfZssERxeMS3FpMP7H0psMzC72C2ga3fqr_Qh88M75A@mail.gmail.com>

On Fri, Jan 12, 2024 at 11:42 AM Nhat Pham <nphamcs@gmail.com> wrote:
>
> On Fri, Jan 12, 2024 at 11:31 AM 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.
>
> 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.