Re: [ANNOUNCEMENT] io_uring SQPOLL sharing changes

[Joseph Qi <joseph.qi@linux.alibaba.com>]

On 3/22/21 10:49 PM, Jens Axboe wrote:
> On 3/21/21 11:54 PM, Xiaoguang Wang wrote:
>> hi Pavel,
>>
>>> Hey,
>>>
>>> You may have already noticed, but there will be a change how SQPOLL
>>> is shared in 5.12. In particular, SQPOLL may be shared only by processes
>>> belonging to the same thread group. If this condition is not fulfilled,
>>> then it silently creates a new SQPOLL task.
>>
>> Thanks for your kindly reminder, currently we only share sqpoll thread
>> in threads belonging to one same process.
> 
> That's good to know, imho it is also the only thing that _really_ makes
> sense to do.
> 
> Since we're on the topic, are you actively using the percpu thread setup
> that you sent out patches for earlier? That could still work within
> the new scheme of having io threads, but I'd be curious to know first
> if you guys are actually using it.
> 

Yes, we've already used percpu sqthread feature in our production
environment, in which 16 application threads share the same sqthread,
and it gains ~20% rt improvement compared with libaio.

Thanks,
Joseph