Re: [PATCH v1 00/15] io_uring zero copy rx

Jens Axboe
2024-10-09T16:12:24Z

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