Re: [PATCH 2/2] io_uring: do the sqpoll napi busy poll outside the submission block

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

On 8/2/24 15:22, Olivier Langlois wrote:
> On Fri, 2024-08-02 at 12:14 +0100, Pavel Begunkov wrote:
>>
>> io_do_sqpoll_napi() returns 1 as long as there are napis in the list,
>> iow even if there is no activity it'll spin almost forever (60s is
>> forever) bypassing sq_thread_idle.
>>
>> Let's not update sqt_spin here, if the user wants it to poll for
>> longer it can pass a larger SQPOLL idle timeout value.
>>
>>
>>
> fair enough...
> 
> in that case, maybe the man page SQPOLL idle timeout description should
> include the mention that if NAPI busy loop is used, the idle timeout
> should be at least as large as gro_flush_timeout to meet NAPI
> requirement to not generate interrupts as described in

Would be great to have, I agree. We might also need to start
a tips and tricks document, not like many people are looking at
documentation.


> Documentation/networking/napi.rst
> section "Software IRQ coalescing"
> 
> I have discovered this fact the hard way by having spent days to figure
> out how to do busy poll the right way.
> 
> this simple mention could save the trouble to many new users of the
> feature.
> 
> I'll rework the patch and send a new version in the few days.

Awesome, thanks

-- 
Pavel Begunkov