Commit e944475e authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: make poll->wait dynamically allocated 



In the quest to bring io_kiocb down to 3 cachelines, this one does
the trick. Make the wait_queue_entry for the poll command come out
of kmalloc instead of embedding it in struct io_poll_iocb, as the
latter is the largest member of io_kiocb. Once we trim this down a
bit, we're back at a healthy 192 bytes for struct io_kiocb.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 6206f0e1

fs/io_uring.c

+17 −12
Original line number Diff line number Diff line
@@ -291,7 +291,7 @@ struct io_poll_iocb { 
	__poll_t			events;

	bool				done;

	bool				canceled;

	struct wait_queue_entry		wait;

	struct wait_queue_entry		*wait;

};



struct io_timeout_data {
@@ -2030,8 +2030,8 @@ static void io_poll_remove_one(struct io_kiocb *req) 


	spin_lock(&poll->head->lock);

	WRITE_ONCE(poll->canceled, true);

	if (!list_empty(&poll->wait.entry)) {

		list_del_init(&poll->wait.entry);

	if (!list_empty(&poll->wait->entry)) {

		list_del_init(&poll->wait->entry);

		io_queue_async_work(req);

	}

	spin_unlock(&poll->head->lock);
@@ -2104,6 +2104,7 @@ static void io_poll_complete(struct io_kiocb *req, __poll_t mask, int error) 
	struct io_ring_ctx *ctx = req->ctx;



	req->poll.done = true;

	kfree(req->poll.wait);

	if (error)

		io_cqring_fill_event(req, error);

	else
@@ -2141,7 +2142,7 @@ static void io_poll_complete_work(struct io_wq_work **workptr) 
	 */

	spin_lock_irq(&ctx->completion_lock);

	if (!mask && ret != -ECANCELED) {

		add_wait_queue(poll->head, &poll->wait);

		add_wait_queue(poll->head, poll->wait);

		spin_unlock_irq(&ctx->completion_lock);

		return;

	}
@@ -2161,8 +2162,7 @@ static void io_poll_complete_work(struct io_wq_work **workptr) 
static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,

			void *key)

{

	struct io_poll_iocb *poll = container_of(wait, struct io_poll_iocb,

							wait);

	struct io_poll_iocb *poll = wait->private;

	struct io_kiocb *req = container_of(poll, struct io_kiocb, poll);

	struct io_ring_ctx *ctx = req->ctx;

	__poll_t mask = key_to_poll(key);
@@ -2172,7 +2172,7 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, 
	if (mask && !(mask & poll->events))

		return 0;



	list_del_init(&poll->wait.entry);

	list_del_init(&poll->wait->entry);



	/*

	 * Run completion inline if we can. We're using trylock here because
@@ -2213,7 +2213,7 @@ static void io_poll_queue_proc(struct file *file, struct wait_queue_head *head, 


	pt->error = 0;

	pt->req->poll.head = head;

	add_wait_queue(head, &pt->req->poll.wait);

	add_wait_queue(head, pt->req->poll.wait);

}



static void io_poll_req_insert(struct io_kiocb *req)
@@ -2252,6 +2252,10 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe, 
	if (!poll->file)

		return -EBADF;



	poll->wait = kmalloc(sizeof(*poll->wait), GFP_KERNEL);

	if (!poll->wait)

		return -ENOMEM;



	req->sqe = NULL;

	INIT_IO_WORK(&req->work, io_poll_complete_work);

	events = READ_ONCE(sqe->poll_events);
@@ -2268,8 +2272,9 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe, 
	ipt.error = -EINVAL; /* same as no support for IOCB_CMD_POLL */



	/* initialized the list so that we can do list_empty checks */

	INIT_LIST_HEAD(&poll->wait.entry);

	init_waitqueue_func_entry(&poll->wait, io_poll_wake);

	INIT_LIST_HEAD(&poll->wait->entry);

	init_waitqueue_func_entry(poll->wait, io_poll_wake);

	poll->wait->private = poll;



	INIT_LIST_HEAD(&req->list);
@@ -2278,14 +2283,14 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe, 
	spin_lock_irq(&ctx->completion_lock);

	if (likely(poll->head)) {

		spin_lock(&poll->head->lock);

		if (unlikely(list_empty(&poll->wait.entry))) {

		if (unlikely(list_empty(&poll->wait->entry))) {

			if (ipt.error)

				cancel = true;

			ipt.error = 0;

			mask = 0;

		}

		if (mask || ipt.error)

			list_del_init(&poll->wait.entry);

			list_del_init(&poll->wait->entry);

		else if (cancel)

			WRITE_ONCE(poll->canceled, true);

		else if (!poll->done) /* actually waiting for an event */

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