Forgot to mention, that this is on 5.7.12, with writev/read during operations. On Mon, 17 Aug 2020 at 14:46, Dmitry Shulyak <yashulyak@xxxxxxxxx> wrote: > > Hi everyone, > > I noticed in iotop that all writes are executed by the same thread > (io_wqe_worker-0). This is a significant problem if I am using files > with mentioned flags. Not the case with reads, requests are > multiplexed over many threads (note the different name > io_wqe_worker-1). The problem is not specific to O_SYNC, in the > general case I can get higher throughput with thread pool and regular > system calls, but specifically with O_SYNC the throughput is the same > as if I were using a single thread for writing. > > The setup is always the same, ring per thread with shared workers pool > (IORING_SETUP_ATTACH_WQ), and high submission rate. Also, it is > possible to get around this performance issue by using separate worker > pools, but then I have to load balance workload between many rings for > perf gains. > > I thought that it may have something to do with the IOSQE_ASYNC flag, > but setting it had no effect. > > Is it expected behavior? Are there any other solutions, except > creating many rings with isolated worker pools?
