From: Wenwen Chen wenwen.chen@samsung.com
[ Upstream commit 533ab73f5b5c95dcb4152b52d5482abcc824c690 ]
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: Kanchan Joshijoshi.k@samsung.com Signed-off-by: Wenwen Chenwenwen.chen@samsung.com Link: https://lore.kernel.org/r/20230525082626.577862-1-wenwen.chen@samsung.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- io_uring/sqpoll.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c index 559652380672c..6ffa5cf1bbb86 100644 --- a/io_uring/sqpoll.c +++ b/io_uring/sqpoll.c @@ -256,9 +256,13 @@ 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; }