Commits on Feb 11, 2024

1. reactor: io_uring: enable some optimization flags …

   Enable some optimization flags in an attempt to improve performance
   with io_uring:
   
   IORING_SETUP_COOP_TASKRUN - prevents a completion from interrupting the
   reactor if it is running. Requires that the reactor issue an io_uring_enter
   system call in a timely fashion, but thanks to the task quota timer, we do.
   
   IORING_SETUP_TASKRUN_FLAG - sets up a flag that notifies the reactor
   that the kernel has pending completions that it did not process. This
   allows the reactor to issue an io_uring_enter even if it has no pending
   submission queue entries or completion queue entries (e.g. it indicates
   a third queue, in the kernel, is not empty).
   
   IORING_SETUP_SINGLE_ISSUER - elides some locking by guaranteeing that only
   a single thread plays with the ring; this happens to be true for us.
   
   IORING_SETUP_DEFER_TASKRUN - batches up completion processing in an
   attempt to get some more performance.
   
   This flags bump up the dependencies to Linux 6.1 and liburing 2.2. This
   seems worthwhile as right now io-uring lags behind linux-aio (which processes
   completions from interrupt context and therefore doesn't need all these
   optimizations).
   
   After this exercise, io_uring is still slower than linux-aio.

   

   avikivity committed Feb 11, 2024
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