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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org
Subject: [RFC 0/2] 3 cacheline io_kiocb
Date: Sat, 25 Jul 2020 11:31:21 +0300
Message-ID: <cover.1595664743.git.asml.silence@gmail.com> (raw)

That's not final for a several reasons, but good enough for discussion.
That brings io_kiocb down to 192B. I didn't try to benchmark it
properly, but quick nop test gave +5% throughput increase.
7531 vs 7910 KIOPS with fio/t/io_uring

The whole situation is obviously a bunch of tradeoffs. For instance,
instead of shrinking it, we can inline apoll to speed apoll path.

[2/2] just for a reference, I'm thinking about other ways to shrink it.
e.g. ->link_list can be a single-linked list with linked tiemouts
storing a back-reference. This can turn out to be better, because
that would move ->fixed_file_refs to the 2nd cacheline, so we won't
ever touch 3rd cacheline in the submission path.
Any other ideas?

note: on top of for-5.9/io_uring,
f56040b819998 ("io_uring: deduplicate io_grab_files() calls")

Pavel Begunkov (2):
  io_uring: allocate req->work dynamically
  io_uring: unionise ->apoll and ->work

 fs/io-wq.h    |   1 +
 fs/io_uring.c | 207 ++++++++++++++++++++++++++------------------------
 2 files changed, 110 insertions(+), 98 deletions(-)

-- 
2.24.0


             reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-25  8:31 Pavel Begunkov [this message]
2020-07-25  8:31 ` [PATCH 1/2] io_uring: allocate req->work dynamically Pavel Begunkov
2020-07-25  8:31 ` [PATCH 2/2] io_uring: unionise ->apoll and ->work Pavel Begunkov
2020-07-25 15:45 ` [RFC 0/2] 3 cacheline io_kiocb Jens Axboe
2020-07-25 18:24   ` Pavel Begunkov
2020-07-25 19:40     ` Jens Axboe
2020-07-25 20:14       ` Pavel Begunkov
2020-07-25 20:25         ` Jens Axboe

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