Messages in this thread | | | From | Usama Arif <> | Subject | [PATCH v6 0/5] io_uring: remove ring quiesce in io_uring_register | Date | Fri, 4 Feb 2022 14:51:12 +0000 |
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Ring quiesce is currently used for registering/unregistering eventfds, registering restrictions and enabling rings.
For opcodes relating to registering/unregistering eventfds, ring quiesce can be avoided 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.
IORING_SETUP_R_DISABLED prevents submitting requests and so there will be no requests until IORING_REGISTER_ENABLE_RINGS is called. And IORING_REGISTER_RESTRICTIONS works only before IORING_REGISTER_ENABLE_RINGS is called. Hence ring quiesce is not needed for these opcodes.
--- v5->v6: - Split removing ring quiesce completely from io_uring_register into 2 patches (Pavel Begunkov) - Removed extra mutex while registering/unregistering eventfd as uring_lock can be used (Pavel Begunkov) - Move setting ctx->evfd to NULL from io_eventfd_put to before call_rcu (Pavel Begunkov)
v4->v5: - Remove ring quiesce completely from io_uring_register (Pavel Begunkov) - Replaced rcu_barrier with unregistering flag (Jens Axboe) - Created a faster check for ctx->io_ev_fd in io_eventfd_signal and cleaned up io_eventfd_unregister (Jens Axboe)
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 (5): io_uring: remove trace for eventfd io_uring: avoid ring quiesce while registering/unregistering eventfd io_uring: avoid ring quiesce while registering async eventfd io_uring: avoid ring quiesce while registering restrictions and enabling rings io_uring: remove ring quiesce for io_uring_register
fs/io_uring.c | 179 +++++++++++++------------------- include/trace/events/io_uring.h | 13 +-- 2 files changed, 75 insertions(+), 117 deletions(-)
-- 2.25.1
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