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| author |   Pavel Begunkov <asml.silence@gmail.com> | 2019-11-21 21:24:56 +0300 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2019-11-25 19:56:10 -0700 |
| commit | 9835d6fafba58e6d9386a6d5af800789bdb52e5b (patch) | |
| tree | 1ff0d914ab1d5b612ff899e987eb16d7ffd3cfca /fs | |
| parent | io_uring: rename __io_submit_sqe() (diff) | |
| download | linux-dev-9835d6fafba58e6d9386a6d5af800789bdb52e5b.tar.xz linux-dev-9835d6fafba58e6d9386a6d5af800789bdb52e5b.zip | |
io_uring: add likely/unlikely in io_get_sqring()
The number of SQEs to submit is specified by a user, so io_get_sqring()
in most of the cases succeeds. Hint compilers about that.
Checking ASM genereted by gcc 9.2.0 for x64, there is one branch
misprediction.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/io_uring.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c index 956a61cb0b13..63e0448f3f8d 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -3129,11 +3129,11 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) */ head = ctx->cached_sq_head; /* make sure SQ entry isn't read before tail */ - if (head == smp_load_acquire(&rings->sq.tail)) + if (unlikely(head == smp_load_acquire(&rings->sq.tail))) return false; head = READ_ONCE(sq_array[head & ctx->sq_mask]); - if (head < ctx->sq_entries) { + if (likely(head < ctx->sq_entries)) { s->ring_file = NULL; s->sqe = &ctx->sq_sqes[head]; s->sequence = ctx->cached_sq_head; |