Commit 533ab73f authored by Wenwen Chen's avatar Wenwen Chen Committed by Jens Axboe
Browse files

io_uring: unlock sqd->lock before sq thread release CPU 



The sq thread actively releases CPU resources by calling the
cond_resched() and schedule() interfaces when it is idle. Therefore,
more resources are available for other threads to run.

There exists a problem in sq thread: it does not unlock sqd->lock before
releasing CPU resources every time. This makes other threads pending on
sqd->lock for a long time. For example, the following interfaces all
require sqd->lock: io_sq_offload_create(), io_register_iowq_max_workers()
and io_ring_exit_work().

Before the sq thread releases CPU resources, unlocking sqd->lock will
provide the user a better experience because it can respond quickly to
user requests.

Signed-off-by: default avatarKanchan <Joshi&lt;joshi.k@samsung.com>
Signed-off-by: default avatarWenwen <Chen&lt;wenwen.chen@samsung.com>
Link: https://lore.kernel.org/r/20230525082626.577862-1-wenwen.chen@samsung.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 293007b0

io_uring/sqpoll.c

+5 −1
Original line number Diff line number Diff line
@@ -255,9 +255,13 @@ static int io_sq_thread(void *data) 
			sqt_spin = true;



		if (sqt_spin || !time_after(jiffies, timeout)) {

			cond_resched();

			if (sqt_spin)

				timeout = jiffies + sqd->sq_thread_idle;

			if (unlikely(need_resched())) {

				mutex_unlock(&sqd->lock);

				cond_resched();

				mutex_lock(&sqd->lock);

			}

			continue;

		}