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    Subject[PATCH v4 0/3] io_uring: avoid ring quiesce in io_uring_register for eventfd opcodes
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    This is done by creating a new RCU data structure (io_ev_fd) as part of
    io_ring_ctx that holds the eventfd_ctx, with reads to the structure protected
    by rcu_read_lock and writes (register/unregister calls) protected by a mutex.

    With the above approach ring quiesce can be avoided which is much more
    expensive then using RCU lock. On the system tested, io_uring_reigster with
    IORING_REGISTER_EVENTFD takes less than 1ms with RCU lock, compared to 15ms
    before with ring quiesce.

    The first patch creates the RCU protected data structure and removes ring
    quiesce for IORING_REGISTER_EVENTFD and IORING_UNREGISTER_EVENTFD.

    The second patch builds on top of the first patch and removes ring quiesce
    for IORING_REGISTER_EVENTFD_ASYNC.

    ---
    v3->v4:
    - Switch back to call_rcu and use rcu_barrier incase io_eventfd_register fails
    to make sure all rcu callbacks have finished.

    v2->v3:
    - Switched to using synchronize_rcu from call_rcu in io_eventfd_unregister.

    v1->v2:
    - Added patch to remove eventfd from tracepoint (Patch 1) (Jens Axboe)
    - Made the code of io_should_trigger_evfd as part of io_eventfd_signal (Jens Axboe)

    Usama Arif (3):
    io_uring: remove trace for eventfd
    io_uring: avoid ring quiesce while registering/unregistering eventfd
    io_uring: avoid ring quiesce for IORING_REGISTER_EVENTFD_ASYNC

    fs/io_uring.c | 127 +++++++++++++++++++++++---------
    include/trace/events/io_uring.h | 13 ++--
    2 files changed, 96 insertions(+), 44 deletions(-)

    --
    2.25.1

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