Re: napi_busy_poll

[Jens Axboe <axboe@kernel.dk>]

On 2/12/22 12:51 PM, Olivier Langlois wrote:
> On Wed, 2022-02-09 at 11:34 +0800, Hao Xu wrote:
>> 在 2022/2/9 上午1:05, Jens Axboe 写道:
>>> On 2/8/22 7:58 AM, Olivier Langlois wrote:
>>>> Hi,
>>>>
>>>> I was wondering if integrating the NAPI busy poll for socket fds
>>>> into
>>>> io_uring like how select/poll/epoll are doing has ever been
>>>> considered?
>>>>
>>>> It seems to me that it could be an awesome feature when used
>>>> along with
>>>> a io_qpoll thread and something not too difficult to add...
>>>
>>> Should be totally doable and it's been brought up before, just
>>> needs
>>> someone to actually do it... Would love to see it.
>>>
>> We've done some investigation before, would like to have a try.
>>
> Hao,
> 
> Let me know if I can help you with coding or testing. I have done very
> preliminary investigation too. It doesn't seem like it would be very
> hard to implement but I get confused with small details.
> 
> For instance, the epoll implementation, unless there is something that
> I don't understand, appears to have a serious limitation. It seems
> like it would not work correctly if there are sockets associated to
> more than 1 NAPI device in the fd set. As far as I am concerned, that
> limitation would be ok since in my setup I only use 1 device but if it
> was necessary to be better than the epoll implementation, I am not
> sure at all how this could be addressed. I do not have enough kernel
> dev experience to find easy solutions to those type of issues...
> 
> Worse case scenario, I guess that I could give it a shot creating a
> good enough implementation for my needs and show it to the list to get
> feedback...

That is, in fact, usually the best way to get feedback on a change! I
believe there's even a law named for it, though local to Linux I
attribute it to akpm. Hence I'd encourage you to do that, best and
fastest way to make progress on the solution.

-- 
Jens Axboe