Commit ebd0df2e authored Jun 17, 2021 by Pavel Begunkov Committed by Jens Axboe Jun 18, 2021

io_uring: optimise task_work submit flushing

tctx_task_work() tries to fetch a next batch of requests, but before it
would flush completions from the previous batch that may be sub-optimal.
E.g. io_req_task_queue() executes a head of the link where all the
linked may be enqueued through the same io_req_task_queue(). And there
are more cases for that.

Do the flushing at the end, so it can cache completions of several waves
of a single tctx_task_work(), and do the flush at the very end.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3cac83934e4fbce520ff8025c3524398b3ae0270.1623949695.git.asml.silence@gmail.com

Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 3f18407d

fs/io_uring.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -1890,13 +1890,13 @@ static void ctx_flush_and_put(struct io_ring_ctx *ctx)

		static void tctx_task_work(struct callback_head *cb)
		{
		struct io_ring_ctx *ctx = NULL;
		struct io_uring_task *tctx = container_of(cb, struct io_uring_task,
		task_work);

		clear_bit(0, &tctx->task_state);

		while (!wq_list_empty(&tctx->task_list)) {
		struct io_ring_ctx *ctx = NULL;
		struct io_wq_work_list list;
		struct io_wq_work_node *node;

		@@ -1920,11 +1920,12 @@ static void tctx_task_work(struct callback_head *cb)
		node = next;
		}

		ctx_flush_and_put(ctx);
		if (!list.first)
		break;
		cond_resched();
		}

		ctx_flush_and_put(ctx);
		}

		static int io_req_task_work_add(struct io_kiocb *req)