Messages in this thread | | | From | Usama Arif <> | Subject | [PATCH v4 0/3] io_uring: avoid ring quiesce in io_uring_register for eventfd opcodes | Date | Thu, 3 Feb 2022 18:24:38 +0000 |
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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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