Re: [Qemu-devel] [PATCH 3/3] linux-aio: process completions from ioq_submit()

[Roman Penyaev]

On Tue, Jul 19, 2016 at 1:47 PM, Paolo Bonzini <address@hidden> wrote:
>
>
> On 19/07/2016 13:44, Roman Penyaev wrote:
>>>> >>
>>>> >> Can this leave I/O stuck if in_queue > 0 && in_flight == 0 after the
>>>> >> return from qemu_laio_process_completions?  I think you need to goto the
>>>> >> beginning of the function to submit more I/O requests in that case.
>> Not quite.  I still leave '&s->e' as set, so we will return in a generic
>> qemu_laio_completion_cb(), will do 'event_notifier_test_and_clear(&s->e)'
>> and again will process events with normal submission.
>>
>> IMHO this is better variant than spinning inside ioq_submit doing goto.
>> We do not occupy the whole events processing for our IO needs and give
>> a chance to complete other stuff.  But of course this is guts feeling
>> and I do not have any serious numbers.
>
> That's fine as long as it doesn't hang. :)

Yeah, but of course would be nice to have it also as fast as possible.
I would say "not to hang as fast as possible" :)

I will write the big comment there why we leave everything as-is
and do not touch the eventfd.  Seems should be fine.

Will send shortly.

--
Roman