[Qemu-devel] [PATCH v3 0/7] aio: Support epoll by introducing qemu_poll abstraction

[Fam Zheng <famz@redhat.com>]

v3: Rebase to master for 2.4.
    Although epoll_pwait1 syscall is still being worked on [1], the QEMU part
    (if any) will base on this, so let's merge it first.
    
    That part is not included in this version because I'm still evaluating by
    comparing epoll_pwait1 with epoll+timerfd as with current master they seem
    to be really close.

    [1]: http://www.spinics.net/lists/linux-api/msg08216.html

v2: Emulate nanoseconds precison of timeout with ppoll and timerfd.
    Their performance is on par with each other, but both much better than
    qemu.git:

    syscall         high # of fd      low # of fd
    -------------------------------------------------
    qemu.git(ppoll) 44                96
    ppoll+epoll     85                101
    timerfd+epoll   87                109

(In high # of fd case, 3 activated but idle virtio-console devices are
attached, which will add us hundereds of fds to poll)

v1 cover letter
---------------

ppoll(2) doesn't scale as well as epoll: The elapsed time of the syscall is
linear to the number of fd's we poll, which hurts performance a bit when the
number of devices are many, or when a virtio device registers many virtqueues
(virtio-serial, for instance).

This series introduces qemu_poll, which is implemented  with g_poll and epoll,
decided at configure time with CONFIG_EPOLL.

Fam


Fam Zheng (7):
  poll: Introduce QEMU Poll API
  posix-aio: Use QEMU poll interface
  poll: Add epoll implementation for qemu_poll
  main-loop: Replace qemu_poll_ns with qemu_poll
  tests: Add test case for qemu_poll
  poll-glib: Support ppoll
  poll-linux: Add timerfd support

 Makefile.objs           |   2 +
 aio-posix.c             |  52 ++++----
 async.c                 |   5 +-
 include/block/aio.h     |   7 +-
 include/qemu/poll.h     |  40 ++++++
 include/qemu/timer.h    |  13 --
 include/qemu/typedefs.h |   4 +-
 main-loop.c             |  35 +++++-
 poll-glib.c             | 153 +++++++++++++++++++++++
 poll-linux.c            | 314 ++++++++++++++++++++++++++++++++++++++++++++++++
 qemu-timer.c            |  28 -----
 tests/Makefile          |   2 +
 tests/test-poll.c       | 272 +++++++++++++++++++++++++++++++++++++++++
 13 files changed, 845 insertions(+), 82 deletions(-)
 create mode 100644 include/qemu/poll.h
 create mode 100644 poll-glib.c
 create mode 100644 poll-linux.c
 create mode 100644 tests/test-poll.c

-- 
1.9.3