From 6962980947e2b967ab26bfd34004b6b573597513 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Fri, 24 Sep 2021 22:00:01 +0100 Subject: [PATCH] io_uring: restructure submit sqes to_submit checks Put an explicit check for number of requests to submit. First, we can turn while into do-while and it generates better code, and second that if can be cheaper, e.g. by using CPU flags after sub in io_sqring_entries(). Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/5926baadd20c28feab7a5e1725fedf32e4553ff7.1632516769.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- fs/io_uring.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index bbb2a26..b8f60cf 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7225,16 +7225,19 @@ static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx) static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr) __must_hold(&ctx->uring_lock) { + unsigned int entries = io_sqring_entries(ctx); int submitted = 0; + if (!entries) + return 0; /* make sure SQ entry isn't read before tail */ - nr = min3(nr, ctx->sq_entries, io_sqring_entries(ctx)); + nr = min3(nr, ctx->sq_entries, entries); if (!percpu_ref_tryget_many(&ctx->refs, nr)) return -EAGAIN; io_get_task_refs(nr); io_submit_state_start(&ctx->submit_state, nr); - while (submitted < nr) { + do { const struct io_uring_sqe *sqe; struct io_kiocb *req; @@ -7253,7 +7256,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr) submitted++; if (io_submit_sqe(ctx, req, sqe)) break; - } + } while (submitted < nr); if (unlikely(submitted != nr)) { int ref_used = (submitted == -EAGAIN) ? 0 : submitted; -- 2.7.4