linux-kernel - [PATCH v2 0/3] io_uring: register single issuer task at creation

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Date:   Mon, 26 Sep 2022 10:09:24 -0700
From:   Dylan Yudaken <dylany@...com>
To:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>
CC:     <io-uring@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kernel-team@...com>, Dylan Yudaken <dylany@...com>
Subject: [PATCH v2 0/3] io_uring: register single issuer task at creation

Registering the single issuer task from the first submit adds unnecesary
complications to the API as well as the implementation. Where simply
registering it at creation should not impose any barriers to getting the
same performance wins. The only catch is users that might want to move the
ring after creation but before submission. For these users allow them to
create the ring with IORING_SETUP_R_DISABLED and then enable it on the
submission task.

There is another problem in 6.1, with IORING_SETUP_DEFER_TASKRUN. That
would like to check the submitter_task from unlocked contexts, which would
be racy. If upfront the submitter_task is set at creation time it will
simplify the logic there and probably increase performance (though this is
unmeasured).

Patch 1 registers the task at creation of the io_uring, this works
standalone in case you want to only merge this part for 6.0

Patch 2/3 cleans up the code from the old style

v2:
 - add the IORING_SETUP_R_DISABLED logic

Dylan Yudaken (3):
  io_uring: register single issuer task at creation
  io_uring: simplify __io_uring_add_tctx_node
  io_uring: remove io_register_submitter

 io_uring/io_uring.c |  9 ++++++++-
 io_uring/tctx.c     | 42 ++++++++++++++++++------------------------
 io_uring/tctx.h     |  6 ++++--
 3 files changed, 30 insertions(+), 27 deletions(-)

base-commit: f76349cf41451c5c42a99f18a9163377e4b364ff
-- 
2.30.2