[PATCH 5.14 00/12] for-next optimisations

Pavel Begunkov
2021-06-14T22:39:09Z

There are two main lines intervened. The first one is pt.2 of ctx field
shuffling for better caching. There is a couple of things left on that
front.

The second is optimising (assumably) rarely used offset-based timeouts
and draining. There is a downside (see 12/12), which will be fixed
later. In plans to queue a task_work clearing drain_used (under
uring_lock) from io_queue_deferred() once all drainee are gone.

nops(batch=32):
15.9 MIOPS vs 17.3 MIOPS
nullblk (irqmode=2 completion_nsec=0 submit_queues=16), no merges, no stat
1002 KIOPS vs 1050 KIOPS

Though the second test is very slow comparing to what I've seen before,
so might be not represantative.

Pavel Begunkov (12):
io_uring: keep SQ pointers in a single cacheline
io_uring: move ctx->flags from SQ cacheline
io_uring: shuffle more fields into SQ ctx section
io_uring: refactor io_get_sqe()
io_uring: don't cache number of dropped SQEs
io_uring: optimise completion timeout flushing
io_uring: small io_submit_sqe() optimisation
io_uring: clean up check_overflow flag
io_uring: wait heads renaming
io_uring: move uring_lock location
io_uring: refactor io_req_defer()
io_uring: optimise non-drain path

fs/io_uring.c | 226 +++++++++++++++++++++++++-------------------------
1 file changed, 111 insertions(+), 115 deletions(-)

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2.31.1