From: Pavel Begunkov <[email protected]>
To: Usama Arif <[email protected]>,
[email protected], [email protected],
[email protected]
Cc: [email protected]
Subject: Re: [PATCH v5 0/4] io_uring: remove ring quiesce in io_uring_register
Date: Fri, 4 Feb 2022 00:02:08 +0000 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 2/3/22 23:34, Usama Arif wrote:
> For opcodes relating to registering/unregistering eventfds, 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 second patch creates the RCU protected data structure and removes ring
> quiesce for IORING_REGISTER_EVENTFD and IORING_UNREGISTER_EVENTFD.
>
> The third patch builds on top of the second patch and removes ring quiesce
> for IORING_REGISTER_EVENTFD_ASYNC.
>
> The fourth patch completely removes ring quiesce from io_uring_register,
> as IORING_REGISTER_ENABLE_RINGS and IORING_REGISTER_RESTRICTIONS dont need
> them.
Let me leave it just for history: I strongly dislike it considering
there is no one who uses or going to use it. Even more, I can't find a
single user of io_uring_unregister_eventfd() in liburing tests, so most
probably the paths are not tested at all.
> ---
> 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 (4):
> 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
> io_uring: remove ring quiesce for io_uring_register
>
> fs/io_uring.c | 202 ++++++++++++++++----------------
> include/trace/events/io_uring.h | 13 +-
> 2 files changed, 107 insertions(+), 108 deletions(-)
>
--
Pavel Begunkov
next prev parent reply other threads:[~2022-02-04 0:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 23:34 [PATCH v5 0/4] io_uring: remove ring quiesce in io_uring_register Usama Arif
2022-02-03 23:34 ` [PATCH v5 1/4] io_uring: remove trace for eventfd Usama Arif
2022-02-03 23:34 ` [PATCH v5 2/4] io_uring: avoid ring quiesce while registering/unregistering eventfd Usama Arif
2022-02-03 23:46 ` Pavel Begunkov
2022-02-03 23:54 ` Pavel Begunkov
2022-02-04 0:12 ` Jens Axboe
2022-02-03 23:34 ` [PATCH v5 3/4] io_uring: avoid ring quiesce for IORING_REGISTER_EVENTFD_ASYNC Usama Arif
2022-02-03 23:34 ` [PATCH v5 4/4] io_uring: remove ring quiesce for io_uring_register Usama Arif
2022-02-03 23:47 ` Pavel Begunkov
2022-02-04 0:28 ` Pavel Begunkov
2022-02-04 0:02 ` Pavel Begunkov [this message]
2022-02-04 0:15 ` [PATCH v5 0/4] io_uring: remove ring quiesce in io_uring_register Jens Axboe
2022-02-04 0:24 ` Pavel Begunkov
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