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. --- 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 | 124 ++++++++++++++++++++++---------- include/trace/events/io_uring.h | 13 ++-- 2 files changed, 93 insertions(+), 44 deletions(-) -- 2.25.1
