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 <sgarzare@xxxxxxxxxx> >> >> 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
