netdev - Re: [RFC v4 00/18] Split netmem from struct page

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Message-ID: <20250609042255.GA43325@system.software.com>
Date: Mon, 9 Jun 2025 13:22:55 +0900
From: Byungchul Park <byungchul@...com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: willy@...radead.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
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Subject: Re: [RFC v4 00/18] Split netmem from struct page

On Thu, Jun 05, 2025 at 12:55:30PM -0700, Mina Almasry wrote:
> On Tue, Jun 3, 2025 at 8:23 PM Byungchul Park <byungchul@...com> wrote:
> >
> > On Wed, Jun 04, 2025 at 11:52:28AM +0900, Byungchul Park 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.  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.
> > >
> > > The final patch removing the page pool fields will be submitted once
> > > all the converting work of page to netmem are done:
> > >
> > >    1. converting of libeth_fqe by Tony Nguyen.
> > >    2. converting of mlx5 by Tariq Toukan.
> > >    3. converting of prueth_swdata (on me).
> > >    4. converting of freescale driver (on me).
> > >
> > > For our discussion, I'm sharing what the final patch looks like the
> > > following.
> >
> > To Willy and Mina,
> >
> > I believe this version might be the final version.  Please check the
> > direction if it's going as you meant so as to go ahead convinced.
> >
> > As I mentioned above, the final patch should be submitted later once all
> > the required works on drivers are done, but you can check what it looks
> > like, in the following embedded patch in this cover letter.
> >
> 
> We need this tested with at least 1 of devmem TCP and io_uring zc to
> make sure the net_iov stuff isn't broken (I'll get to that when I have
> time).
> 
> And we need page_pool benchmark numbers before/after this series,
> please run those yourself, if at all possible:

I'm trying but it keeps conflicting on several steps..  Please share a
better manual.

	Byungchul

> https://lore.kernel.org/netdev/20250525034354.258247-1-almasrymina@google.com/
> 
> This series adds a bunch of netmem/page casts. I expect them not to
> affect fast-path perf, but making sure would be nice.
> 
> -- 
> Thanks,
> Mina