linux-kernel - Re: [RFC 00/19] Split netmem from struct page

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Message-ID: <CAHS8izPFiytN_bM6cu2X8qbvyVTL6pFMeobW=qFwjgHbg5La9Q@mail.gmail.com>
Date: Fri, 9 May 2025 07:09:16 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Byungchul Park <byungchul@...com>, Pavel Begunkov <asml.silence@...il.com>
Cc: willy@...radead.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, kernel_team@...ynix.com, kuba@...nel.org, 
	ilias.apalodimas@...aro.org, harry.yoo@...cle.com, hawk@...nel.org, 
	akpm@...ux-foundation.org, ast@...nel.org, daniel@...earbox.net, 
	davem@...emloft.net, john.fastabend@...il.com, andrew+netdev@...n.ch, 
	edumazet@...gle.com, pabeni@...hat.com, vishal.moola@...il.com
Subject: Re: [RFC 00/19] Split netmem from struct page

On Fri, May 9, 2025 at 4:51 AM Byungchul Park <byungchul@...com> wrote:
>
> The MM subsystem is trying to reduce struct page to a single pointer.
> The first step towards that is splitting struct page by its individual
> users, as has already been done with folio and slab.  This patchset does
> that for netmem which is used for page pools.
>
> Matthew Wilcox tried and stopped the same work, you can see in:
>
>    https://lore.kernel.org/linux-mm/20230111042214.907030-1-willy@infradead.org/
>
> Mina Almasry already has done a lot fo prerequisite works by luck, he
> said :).  I stacked my patches on the top of his work e.i. netmem.
>
> I focused on removing the page pool members in struct page this time,
> not moving the allocation code of page pool from net to mm.  It can be
> done later if needed.
>
> There are still a lot of works to do, to remove the dependency on struct
> page in the network subsystem.  I will continue to work on this after
> this base patchset is merged.
>
> This patchset is based on mm tree's mm-unstable branch.
>

This series largely looks good to me, but a couple of things:

- For deep changes like this to the page_pool, I think we need a
before/after run to Jesper's currently out-of-tree benchmark to see
any regressions:
https://lore.kernel.org/netdev/20250309084118.3080950-1-almasrymina@google.com/

- Also please CC Pavel on iterations related to netmem/net_iov, they
are reusing that in io_uring code for iouring rx rc as well.

--
Thanks,
Mina