Commit 6d63416d authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: optimise plugging 



Plugging is only needed with requests that also need a file, so hide
plugging under a ->needs_file check. Also, place ->needs_file and ->plug
bits into the same byte of io_op_defs, it may matter for compilers, e.g.
only with the change a tested one decided to optimise two memory testb
into a more with two register testb.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1600d1287bb7d16451d4ef3343252787a5314927.1633532552.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 54daa9b2

fs/io_uring.c

+16 −16
Original line number Diff line number Diff line
@@ -894,12 +894,12 @@ struct io_defer_entry { 
struct io_op_def {

	/* needs req->file assigned */

	unsigned		needs_file : 1;

	/* should block plug */

	unsigned		plug : 1;

	/* hash wq insertion if file is a regular file */

	unsigned		hash_reg_file : 1;

	/* unbound wq insertion if file is a non-regular file */

	unsigned		unbound_nonreg_file : 1;

	/* opcode is not supported by this kernel */

	unsigned		not_supported : 1;

	/* set if opcode supports polled "wait" */

	unsigned		pollin : 1;

	unsigned		pollout : 1;
@@ -907,8 +907,8 @@ struct io_op_def { 
	unsigned		buffer_select : 1;

	/* do prep async if is going to be punted */

	unsigned		needs_async_setup : 1;

	/* should block plug */

	unsigned		plug : 1;

	/* opcode is not supported by this kernel */

	unsigned		not_supported : 1;

	/* size of async data needed, if any */

	unsigned short		async_size;

};
@@ -6978,7 +6978,6 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, 
		       const struct io_uring_sqe *sqe)

	__must_hold(&ctx->uring_lock)

{

	struct io_submit_state *state;

	unsigned int sqe_flags;

	int personality;
@@ -7025,19 +7024,20 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, 
		get_cred(req->creds);

		req->flags |= REQ_F_CREDS;

	}

	state = &ctx->submit_state;



	if (io_op_defs[req->opcode].needs_file) {

		struct io_submit_state *state = &ctx->submit_state;



		/*

	 * Plug now if we have more than 1 IO left after this, and the target

	 * is potentially a read/write to block based storage.

		 * Plug now if we have more than 2 IO left after this, and the

		 * target is potentially a read/write to block based storage.

		 */

		if (state->need_plug && io_op_defs[req->opcode].plug) {

		blk_start_plug(&state->plug);

			state->plug_started = true;

			state->need_plug = false;

			blk_start_plug(&state->plug);

		}



	if (io_op_defs[req->opcode].needs_file) {

		req->file = io_file_get(ctx, req, READ_ONCE(sqe->fd),

					(sqe_flags & IOSQE_FIXED_FILE));

		if (unlikely(!req->file))