What’s epoll? - Julia Evans

What’s O_NONBLOCK ? - Blocking I/O, Nonblocking I/O, And Epoll

• select / poll / epoll: practical difference for system architects
  • No new code should be using select()
  • In the vast majority of cases you would be choosing between poll and epoll/libevent.
  • To use epoll, much more preparation is needed.
  • select carries quite a few design flaws which make it undesirable as a polling mechanism in the modern networking application… is there is any reason to use select at all?
    • The first reason is portability.
    • select can - theoretically - handle the timeouts withing the one nanosecond precision, while both poll and epoll can only handle the one millisecond precision.
• Using select(2) - Use libev, Boost.Asio or other libraries.
  • libev - A full-featured and high-performance event loop that is loosely modelled after libevent.

io_uring

• Waiting for many things at once with io_uring
  • Do Files want to be Actors? - using his io_uring test server, like this one[0] claiming 180 GB/s of write throughput, which is fast enough to start blurring the lines with memory bandwidth. You can’t use mmap() for large persistent data because CPU silicon doesn’t support enough virtual memory