Re: [PATCH v6 0/5] io_uring zcrx ifq sharing

[Pavel Begunkov <asml.silence@gmail.com>]

On 11/8/25 18:14, David Wei wrote:
> Each ifq is bound to a HW RX queue with no way to share this across
> multiple rings. It is possible that one ring will not be able to fully
> saturate an entire HW RX queue due to userspace work. There are two ways
> to handle more work:
> 
>    1. Move work to other threads, but have to pay context switch overhead
>       and cold caches.
>    2. Add more rings with ifqs, but HW RX queues are a limited resource.
> 
> This patchset add a way for multiple rings to share the same underlying
> src ifq that is bound to a HW RX queue. Rings with shared ifqs can issue
> io_recvzc on zero copy sockets, just like the src ring.
> 
> Userspace are expected to create rings in separate threads and not
> processes, such that all rings share the same address space. This is
> because the sharing and synchronisation of refill rings is purely done
> in userspace with no kernel involvement e.g. dst rings do not mmap the
> refill ring. Also, userspace must distribute zero copy sockets steered
> into the same HW RX queue across rings sharing the ifq.

I agree it's the simplest way to use it, but cross process sharing
is a valid use case. I'm sure you can mmap it by guessing offset
and you can place it into some shared memory otherwise.

The implementation lgtm. I need to give it a run, but let me
queue it up with other dependencies.

-- 
Pavel Begunkov