From: Jens Axboe <[email protected]>
To: Stefano Garzarella <[email protected]>
Cc: [email protected], [email protected]
Subject: Re: [PATCH liburing 1/1] test: add epoll test case
Date: Mon, 27 Jan 2020 11:46:34 -0700 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <20200127182534.5ljsj53vzpj6kkru@steredhat>
On 1/27/20 11:25 AM, Stefano Garzarella wrote:
> On Mon, Jan 27, 2020 at 09:32:43AM -0700, Jens Axboe wrote:
>> On 1/27/20 9:17 AM, Stefano Garzarella wrote:
>>> Signed-off-by: Stefano Garzarella <[email protected]>
>>
>> You're not reaping CQ events, and hence you overflow the ring. Once
>> overflown, an attempt to submit new IO will returns in a -16/-EBUSY
>> return value. This is io_uring telling you that it won't submit more
>> IO until you've emptied the completion ring so io_uring can flush
>> the overflown entries to the ring.
>
> How can I reaping CQ events? (I was hoping the epoll would help me with that)
>
> What I'm seeing is that the producer (EPOLLOUT) can fill the SQ without issues,
> the consumer (read()) is receiving all the buffers produced, but the thread
> that frees the buffers (EPOLLIN) is not woken up.
>
> I tried to set a timeout to the epoll_wait(), but the io_uring_peek_cqe()
> returns -EAGAIN.
>
> If I'm using a ring with 16 entries, it seems to work better, but
> sometimes I lose events and the thread that frees the buffer doesn't wake up.
>
> Maybe I'm missing something...
OK, so that helps in terms of understanding the issue you are seeing with
it. I'll take a look at this, but it'll probably be a few days. You can
try and enable tracing, I see events completed just fine. Maybe a race
with your epoll wait and event reaping?
--
Jens Axboe
next prev parent reply other threads:[~2020-01-27 18:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-27 16:17 [PATCH liburing 0/1] test: add epoll test case Stefano Garzarella
2020-01-27 16:17 ` [PATCH liburing 1/1] " Stefano Garzarella
2020-01-27 16:32 ` Jens Axboe
2020-01-27 18:25 ` Stefano Garzarella
2020-01-27 18:46 ` Jens Axboe [this message]
2020-01-27 18:50 ` Stefano Garzarella
2020-01-28 13:06 ` Stefano Garzarella
2020-01-27 16:26 ` [PATCH liburing 0/1] " Jens Axboe
2020-01-27 18:00 ` Stefano Garzarella
2020-01-27 18:07 ` Jens Axboe
2020-01-27 18:28 ` Stefano Garzarella
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