Commit 27926b68 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: only plug when appropriate 



We unconditionally call blk_start_plug() when starting the IO
submission, but we only really should do that if we have more than 1
request to submit AND we're potentially dealing with block based storage
underneath. For any other type of request, it's just a waste of time to
do so.

Add a ->plug bit to io_op_def and set it for read/write requests. We
could make this more precise and check the file itself as well, but it
doesn't matter that much and would quickly become more expensive.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 0415767e

fs/io_uring.c

+23 −2
Original line number Diff line number Diff line
@@ -750,6 +750,8 @@ struct io_submit_state { 
	void			*reqs[IO_IOPOLL_BATCH];

	unsigned int		free_reqs;



	bool			plug_started;



	/*

	 * Batch completion logic

	 */
@@ -782,6 +784,8 @@ struct io_op_def { 
	unsigned		buffer_select : 1;

	/* must always have async data allocated */

	unsigned		needs_async_data : 1;

	/* should block plug */

	unsigned		plug : 1;

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

	unsigned short		async_size;

	unsigned		work_flags;
@@ -795,6 +799,7 @@ static const struct io_op_def io_op_defs[] = { 
		.pollin			= 1,

		.buffer_select		= 1,

		.needs_async_data	= 1,

		.plug			= 1,

		.async_size		= sizeof(struct io_async_rw),

		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,

	},
@@ -804,6 +809,7 @@ static const struct io_op_def io_op_defs[] = { 
		.unbound_nonreg_file	= 1,

		.pollout		= 1,

		.needs_async_data	= 1,

		.plug			= 1,

		.async_size		= sizeof(struct io_async_rw),

		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |

						IO_WQ_WORK_FSIZE,
@@ -816,6 +822,7 @@ static const struct io_op_def io_op_defs[] = { 
		.needs_file		= 1,

		.unbound_nonreg_file	= 1,

		.pollin			= 1,

		.plug			= 1,

		.async_size		= sizeof(struct io_async_rw),

		.work_flags		= IO_WQ_WORK_BLKCG | IO_WQ_WORK_MM,

	},
@@ -824,6 +831,7 @@ static const struct io_op_def io_op_defs[] = { 
		.hash_reg_file		= 1,

		.unbound_nonreg_file	= 1,

		.pollout		= 1,

		.plug			= 1,

		.async_size		= sizeof(struct io_async_rw),

		.work_flags		= IO_WQ_WORK_BLKCG | IO_WQ_WORK_FSIZE |

						IO_WQ_WORK_MM,
@@ -907,6 +915,7 @@ static const struct io_op_def io_op_defs[] = { 
		.unbound_nonreg_file	= 1,

		.pollin			= 1,

		.buffer_select		= 1,

		.plug			= 1,

		.async_size		= sizeof(struct io_async_rw),

		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,

	},
@@ -914,6 +923,7 @@ static const struct io_op_def io_op_defs[] = { 
		.needs_file		= 1,

		.unbound_nonreg_file	= 1,

		.pollout		= 1,

		.plug			= 1,

		.async_size		= sizeof(struct io_async_rw),

		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |

						IO_WQ_WORK_FSIZE,
@@ -6585,6 +6595,7 @@ static void io_submit_state_end(struct io_submit_state *state) 
{

	if (!list_empty(&state->comp.list))

		io_submit_flush_completions(&state->comp);

	if (state->plug_started)

		blk_finish_plug(&state->plug);

	io_state_file_put(state);

	if (state->free_reqs)
@@ -6597,7 +6608,7 @@ static void io_submit_state_end(struct io_submit_state *state) 
static void io_submit_state_start(struct io_submit_state *state,

				  struct io_ring_ctx *ctx, unsigned int max_ios)

{

	blk_start_plug(&state->plug);

	state->plug_started = false;

	state->comp.nr = 0;

	INIT_LIST_HEAD(&state->comp.list);

	state->comp.ctx = ctx;
@@ -6739,6 +6750,16 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, 
	/* same numerical values with corresponding REQ_F_*, safe to copy */

	req->flags |= sqe_flags;



	/*

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

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

	 */

	if (!state->plug_started && state->ios_left > 1 &&

	    io_op_defs[req->opcode].plug) {

		blk_start_plug(&state->plug);

		state->plug_started = true;

	}



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

		return 0;

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