netdev - Re: [PATCH v1 00/15] io

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Message-ID: <4e285394-3a07-4946-b7a4-c4e503f9a964@kernel.dk>
Date: Wed, 9 Oct 2024 10:12:22 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Pavel Begunkov <asml.silence@...il.com>, Joe Damato <jdamato@...tly.com>,
 David Wei <dw@...idwei.uk>, io-uring@...r.kernel.org,
 netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jesper Dangaard Brouer
 <hawk@...nel.org>, David Ahern <dsahern@...nel.org>,
 Mina Almasry <almasrymina@...gle.com>
Subject: Re: [PATCH v1 00/15] io_uring zero copy rx

On 10/9/24 9:07 AM, Pavel Begunkov wrote:
> On 10/9/24 00:10, Joe Damato wrote:
>> On Mon, Oct 07, 2024 at 03:15:48PM -0700, David Wei wrote:
>>> This patchset adds support for zero copy rx into userspace pages using
>>> io_uring, eliminating a kernel to user copy.
>>>
>>> We configure a page pool that a driver uses to fill a hw rx queue to
>>> hand out user pages instead of kernel pages. Any data that ends up
>>> hitting this hw rx queue will thus be dma'd into userspace memory
>>> directly, without needing to be bounced through kernel memory. 'Reading'
>>> data out of a socket instead becomes a _notification_ mechanism, where
>>> the kernel tells userspace where the data is. The overall approach is
>>> similar to the devmem TCP proposal.
>>>
>>> This relies on hw header/data split, flow steering and RSS to ensure
>>> packet headers remain in kernel memory and only desired flows hit a hw
>>> rx queue configured for zero copy. Configuring this is outside of the
>>> scope of this patchset.
>>
>> This looks super cool and very useful, thanks for doing this work.
>>
>> Is there any possibility of some notes or sample pseudo code on how
>> userland can use this being added to Documentation/networking/ ?
> 
> io_uring man pages would need to be updated with it, there are tests
> in liburing and would be a good idea to add back a simple exapmle
> to liburing/example/*. I think it should cover it

man pages for sure, but +1 to the example too. Just a basic thing would
get the point across, I think.

-- 
Jens Axboe