[Qemu-block] [PATCH RFC 0/4] aio: Use epoll_wait in aio_poll

[Fam Zheng]

epoll is more scalable than ppoll. It performs faster than ppoll when the
number of polled fds is high.

See patch 4 for an example of the senario and some benchmark data.

Note: it is only effective on iothread (dataplane), while the main loop cannot
benefit from this yet, because the iohandler and chardev GSource's don't easily
fit into this epoll interface style (that's why main loop uses qemu_poll_ns
directly instead of aio_poll()).

There is hardly any timer activity in iothreads for now, as a result the
timeout is always 0 or -1. Therefore, timerfd, or the said nanosecond
epoll_pwait1 interface, which fixes the timeout granularity deficiency is not
immediately necessary at this point, but still that will be simple to add.

Please review!

Fam

Fam Zheng (4):
  aio: Introduce aio_set_fd_handler_pri
  aio: Move aio_set_fd_handler to async.c
  aio: Introduce aio_context_setup
  aio-posix: Use epoll in aio_poll

 aio-posix.c         | 127 +++++++++++++++++++++++++++++++++++++++++++++++-----
 aio-win32.c         |   7 +--
 async.c             |  24 ++++++++--
 include/block/aio.h |   6 +++
 4 files changed, 144 insertions(+), 20 deletions(-)

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2.4.3