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

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Message-ID: <550cf666-ea4f-4dac-9acf-fad448324e87@davidwei.uk>
Date: Thu, 10 Oct 2024 23:15:27 -0700
From: David Wei <dw@...idwei.uk>
To: Jens Axboe <axboe@...nel.dk>, Pavel Begunkov <asml.silence@...il.com>,
 Joe Damato <jdamato@...tly.com>, 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>, David Wei <dw@...idwei.uk>
Subject: Re: [PATCH v1 00/15] io_uring zero copy rx

On 2024-10-09 09:12, Jens Axboe wrote:
> 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.
> 

Yeah, there's the liburing side with helpers and all that which will get
manpages. We'll also put back a simple example demonstrating the uAPI.
The liburing changes will be sent as a separate patchset to the io-uring
list.