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

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Message-ID: <6a45f884-f9d3-4b18-9881-3bfd3a558ea8@gmail.com>
Date: Wed, 9 Oct 2024 16:07:01 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Joe Damato <jdamato@...tly.com>, David Wei <dw@...idwei.uk>,
 io-uring@...r.kernel.org, netdev@...r.kernel.org,
 Jens Axboe <axboe@...nel.dk>, 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 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

-- 
Pavel Begunkov