io_uring: optimise submission left counting

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Considering all inlining io_submit_sqe() is huge and usually ends up
calling some other functions.

We decrement @left in io_submit_sqes() just before calling
io_submit_sqe() and use it later after the call. Considering how huge
io_submit_sqe() is, there is not much hope @left will be treated
gracefully by compilers.

Decrement it after the call, not only it's easier on register spilling
and probably saves stack write/read, but also at least for x64 uses
CPU flags set by the dec instead of doing (read/write and tests).

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/807f9a276b54ee8ff4e42e2b78721484f1c71743.1649771823.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Pavel Begunkov 2022-04-12 15:09:50 +01:00 • committed by Jens Axboe

parent 8e6971a819

commit 1cd15904b6

1 changed files with 10 additions and 10 deletions

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fs/io_uring.c

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