On Sun, Dec 20, 2020 at 12:11 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > > On 12/19/20 9:29 AM, Jens Axboe wrote: > > On 12/19/20 9:13 AM, Jens Axboe wrote: > >> On 12/18/20 7:49 PM, Josef wrote: > >>>> I'm happy to run _any_ reproducer, so please do let us know if you > >>>> manage to find something that I can run with netty. As long as it > >>>> includes instructions for exactly how to run it :-) > >>> > >>> cool :) I just created a repo for that: > >>> https://github.com/1Jo1/netty-io_uring-kernel-debugging.git > >>> > >>> - install jdk 1.8 > >>> - to run netty: ./mvnw compile exec:java > >>> -Dexec.mainClass="uring.netty.example.EchoUringServer" > >>> - to run the echo test: cargo run --release -- --address > >>> "127.0.0.1:2022" --number 200 --duration 20 --length 300 > >>> (https://github.com/haraldh/rust_echo_bench.git) > >>> - process kill -9 > >>> > >>> async flag is enabled and these operation are used: OP_READ, > >>> OP_WRITE, OP_POLL_ADD, OP_CLOSE, OP_ACCEPT > >>> > >>> (btw you can change the port in EchoUringServer.java) > >> > >> This is great! Not sure this is the same issue, but what I see here is > >> that we have leftover workers when the test is killed. This means the > >> rings aren't gone, and the memory isn't freed (and unaccounted), which > >> would ultimately lead to problems of course, similar to just an > >> accounting bug or race. > >> > >> The above _seems_ to be related to IOSQE_ASYNC. Trying to narrow it > >> down... > > > > Further narrowed down, it seems to be related to IOSQE_ASYNC on the > > read requests. I'm guessing there are cases where we end up not > > canceling them on ring close, hence the ring stays active, etc. > > > > If I just add a hack to clear IOSQE_ASYNC on IORING_OP_READ, then > > the test terminates fine on the kill -9. > > And even more so, it's IOSQE_ASYNC on the IORING_OP_READ on an eventfd > file descriptor. In our case - unlike netty - we use io_uring only for disk IO, no eventfd. And we do not use IOSQE_ASYNC (we've tried, but this coincided with some kernel crashes, so we've disabled it for now - not 100% sure if it's related or not yet). I'll try (again) to build a simpler reproducer for our issue, which is probably different from the netty one. -- Dmitry Kadashev
