linux-kernel - Re: [PATCH net-next v6 1/9] netmem: introduce struct netmem

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Message-ID: <3b71cfa9-6c6f-48f7-8457-dac915438216@gmail.com>
Date: Mon, 23 Jun 2025 20:28:31 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Mina Almasry <almasrymina@...gle.com>, Harry Yoo <harry.yoo@...cle.com>
Cc: Byungchul Park <byungchul@...com>, David Hildenbrand <david@...hat.com>,
 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, hawk@...nel.org, akpm@...ux-foundation.org,
 davem@...emloft.net, john.fastabend@...il.com, andrew+netdev@...n.ch,
 toke@...hat.com, tariqt@...dia.com, edumazet@...gle.com, pabeni@...hat.com,
 saeedm@...dia.com, leon@...nel.org, ast@...nel.org, daniel@...earbox.net,
 lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz,
 rppt@...nel.org, surenb@...gle.com, mhocko@...e.com, horms@...nel.org,
 linux-rdma@...r.kernel.org, bpf@...r.kernel.org, vishal.moola@...il.com,
 hannes@...xchg.org, ziy@...dia.com, jackmanb@...gle.com
Subject: Re: [PATCH net-next v6 1/9] netmem: introduce struct netmem_desc
 mirroring struct page

On 6/23/25 20:09, Mina Almasry wrote:
> On Mon, Jun 23, 2025 at 5:18 AM Harry Yoo <harry.yoo@...cle.com> wrote:
>>
>> On Mon, Jun 23, 2025 at 07:28:21PM +0900, Byungchul Park wrote:
>>> On Mon, Jun 23, 2025 at 11:32:16AM +0200, David Hildenbrand wrote:
>>>> On 20.06.25 06:12, Byungchul Park wrote:
>>>>> To simplify struct page, the page pool members of struct page should be
>>>>> moved to other, allowing these members to be removed from struct page.
>>>>>
>>>>> Introduce a network memory descriptor to store the members, struct
>>>>> netmem_desc, and make it union'ed with the existing fields in struct
>>>>> net_iov, allowing to organize the fields of struct net_iov.
>>>>
>>>> It would be great adding some result from the previous discussions in
>>>> here, such as that the layout of "struct net_iov" can be changed because
>>>> it is not a "struct page" overlay, what the next steps based on this
>>>
>>> I think the network folks already know how to use and interpret their
>>> data struct, struct net_iov for sure.. but I will add the comment if it
>>> you think is needed.  Thanks for the comment.
>>
>> I agree with David - it's not immediately obvious at first glance.
>> That was my feedback on the previous version as well :)
>>
>> I think it'd be great to add that explanation, since this is where MM and
>> networking intersect.
>>
> 
> I think a lot of people are now saying the same thing: (1) lets keep
> net_iov and page/netmem_desc separate, and (2) lets add comments
> explaining their relation so this intersection between MM and
> networking is not confused in the long term .
> 
> For #1, concretely I would recommend removing the union inside struct
> net_iov? And also revert all the changes to net_iov for that matter.

Without it the merge logistics will get more complicated than it
should be because of conflicts with changes in the io_uring tree.
It's a temporary solution, I'll convert once the series is merged
and reaches io_uring.

-- 
Pavel Begunkov