io_uring: optimise completion timeout flushing

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io_commit_cqring() might be very hot and we definitely don't want to
touch ->timeout_list there, because 1) it's shared with the submission
side so might lead to cache bouncing and 2) may need to load an extra
cache line, especially for IRQ completions.

We're interested in it at the completion side only when there are
offset-mode timeouts, which are not so popular. Replace
list_empty(->timeout_list) hot path check with a new one-way flag, which
is set when we prepare the first offset-mode timeout.

note: the flag sits in the same line as briefly used after ->rings

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e4892ec68b71a69f92ffbea4a1499be3ec0d463b.1623709150.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Pavel Begunkov 2021-06-14 23:37:25 +01:00 • committed by Jens Axboe

parent 15641e4270

commit f18ee4cf0a

1 changed files with 6 additions and 4 deletions

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fs/io_uring.c

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