Commit 5eef4e87 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: use single linked list for iopoll 



Use single linked lists for keeping iopoll requests, takes less space,
may be faster, but mostly will be of benefit for further patches.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/314033676b100cd485518c3bc55e1b95a0dcd71f.1632516769.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent e3f721e6

fs/io-wq.h

+3 −0
Original line number Diff line number Diff line
@@ -32,6 +32,9 @@ struct io_wq_work_list { 
#define wq_list_for_each(pos, prv, head)			\

	for (pos = (head)->first, prv = NULL; pos; prv = pos, pos = (pos)->next)



#define wq_list_for_each_resume(pos, prv)			\

	for (; pos; prv = pos, pos = (pos)->next)



#define wq_list_empty(list)	(READ_ONCE((list)->first) == NULL)

#define INIT_WQ_LIST(list)	do {				\

	(list)->first = NULL;					\

fs/io_uring.c

+27 −27
Original line number Diff line number Diff line
@@ -412,7 +412,7 @@ struct io_ring_ctx { 
		 * For SQPOLL, only the single threaded io_sq_thread() will

		 * manipulate the list, hence no extra locking is needed there.

		 */

		struct list_head	iopoll_list;

		struct io_wq_work_list	iopoll_list;

		struct hlist_head	*cancel_hash;

		unsigned		cancel_hash_bits;

		bool			poll_multi_queue;
@@ -1309,7 +1309,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) 
	init_waitqueue_head(&ctx->cq_wait);

	spin_lock_init(&ctx->completion_lock);

	spin_lock_init(&ctx->timeout_lock);

	INIT_LIST_HEAD(&ctx->iopoll_list);

	INIT_WQ_LIST(&ctx->iopoll_list);

	INIT_LIST_HEAD(&ctx->defer_list);

	INIT_LIST_HEAD(&ctx->timeout_list);

	INIT_LIST_HEAD(&ctx->ltimeout_list);
@@ -2441,15 +2441,9 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, struct list_head *done) 
	io_req_free_batch_finish(ctx, &rb);

}



/* same as "continue" but starts from the pos, not next to it */

#define list_for_each_entry_safe_resume(pos, n, head, member) 		\

	for (n = list_next_entry(pos, member);				\

	     !list_entry_is_head(pos, head, member);			\

	     pos = n, n = list_next_entry(n, member))



static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)

{

	struct io_kiocb *req, *tmp;

	struct io_wq_work_node *pos, *start, *prev;

	unsigned int poll_flags = BLK_POLL_NOSLEEP;

	DEFINE_IO_COMP_BATCH(iob);

	int nr_events = 0;
@@ -2462,7 +2456,8 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin) 
	if (ctx->poll_multi_queue || force_nonspin)

		poll_flags |= BLK_POLL_ONESHOT;



	list_for_each_entry(req, &ctx->iopoll_list, inflight_entry) {

	wq_list_for_each(pos, start, &ctx->iopoll_list) {

		struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);

		struct kiocb *kiocb = &req->rw.kiocb;

		int ret;
@@ -2488,14 +2483,20 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin) 


	if (!rq_list_empty(iob.req_list))

		iob.complete(&iob);

	list_for_each_entry_safe_resume(req, tmp, &ctx->iopoll_list,

					inflight_entry) {

	else if (!pos)

		return 0;



	prev = start;

	wq_list_for_each_resume(pos, prev) {

		struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);



		if (!READ_ONCE(req->iopoll_completed))

			break;

		list_move_tail(&req->inflight_entry, &done);

		list_add_tail(&req->inflight_entry, &done);

		nr_events++;

	}



	wq_list_cut(&ctx->iopoll_list, prev, start);

	if (nr_events)

		io_iopoll_complete(ctx, &done);

	return nr_events;
@@ -2511,7 +2512,7 @@ static void io_iopoll_try_reap_events(struct io_ring_ctx *ctx) 
		return;



	mutex_lock(&ctx->uring_lock);

	while (!list_empty(&ctx->iopoll_list)) {

	while (!wq_list_empty(&ctx->iopoll_list)) {

		/* let it sleep and repeat later if can't complete a request */

		if (io_do_iopoll(ctx, true) == 0)

			break;
@@ -2560,7 +2561,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min) 
		 * forever, while the workqueue is stuck trying to acquire the

		 * very same mutex.

		 */

		if (list_empty(&ctx->iopoll_list)) {

		if (wq_list_empty(&ctx->iopoll_list)) {

			u32 tail = ctx->cached_cq_tail;



			mutex_unlock(&ctx->uring_lock);
@@ -2569,7 +2570,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min) 


			/* some requests don't go through iopoll_list */

			if (tail != ctx->cached_cq_tail ||

			    list_empty(&ctx->iopoll_list))

			    wq_list_empty(&ctx->iopoll_list))

				break;

		}

		ret = io_do_iopoll(ctx, !min);
@@ -2729,14 +2730,13 @@ static void io_iopoll_req_issued(struct io_kiocb *req) 
	 * how we do polling eventually, not spinning if we're on potentially

	 * different devices.

	 */

	if (list_empty(&ctx->iopoll_list)) {

	if (wq_list_empty(&ctx->iopoll_list)) {

		ctx->poll_multi_queue = false;

	} else if (!ctx->poll_multi_queue) {

		struct io_kiocb *list_req;



		list_req = list_first_entry(&ctx->iopoll_list, struct io_kiocb,

						inflight_entry);



		list_req = container_of(ctx->iopoll_list.first, struct io_kiocb,

					comp_list);

		if (list_req->file != req->file)

			ctx->poll_multi_queue = true;

	}
@@ -2746,9 +2746,9 @@ static void io_iopoll_req_issued(struct io_kiocb *req) 
	 * it to the front so we find it first.

	 */

	if (READ_ONCE(req->iopoll_completed))

		list_add(&req->inflight_entry, &ctx->iopoll_list);

		wq_list_add_head(&req->comp_list, &ctx->iopoll_list);

	else

		list_add_tail(&req->inflight_entry, &ctx->iopoll_list);

		wq_list_add_tail(&req->comp_list, &ctx->iopoll_list);



	if (unlikely(in_async)) {

		/*
@@ -7322,14 +7322,14 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries) 
	if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)

		to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;



	if (!list_empty(&ctx->iopoll_list) || to_submit) {

	if (!wq_list_empty(&ctx->iopoll_list) || to_submit) {

		const struct cred *creds = NULL;



		if (ctx->sq_creds != current_cred())

			creds = override_creds(ctx->sq_creds);



		mutex_lock(&ctx->uring_lock);

		if (!list_empty(&ctx->iopoll_list))

		if (!wq_list_empty(&ctx->iopoll_list))

			io_do_iopoll(ctx, true);



		/*
@@ -7407,7 +7407,7 @@ static int io_sq_thread(void *data) 
		list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {

			int ret = __io_sq_thread(ctx, cap_entries);



			if (!sqt_spin && (ret > 0 || !list_empty(&ctx->iopoll_list)))

			if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))

				sqt_spin = true;

		}

		if (io_run_task_work())
@@ -7428,7 +7428,7 @@ static int io_sq_thread(void *data) 
				io_ring_set_wakeup_flag(ctx);



				if ((ctx->flags & IORING_SETUP_IOPOLL) &&

				    !list_empty_careful(&ctx->iopoll_list)) {

				    !wq_list_empty(&ctx->iopoll_list)) {

					needs_sched = false;

					break;

				}
@@ -9583,7 +9583,7 @@ static void io_uring_try_cancel_requests(struct io_ring_ctx *ctx, 
		/* SQPOLL thread does its own polling */

		if ((!(ctx->flags & IORING_SETUP_SQPOLL) && cancel_all) ||

		    (ctx->sq_data && ctx->sq_data->thread == current)) {

			while (!list_empty_careful(&ctx->iopoll_list)) {

			while (!wq_list_empty(&ctx->iopoll_list)) {

				io_iopoll_try_reap_events(ctx);

				ret = true;

			}