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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: Kanchan Joshi<joshi.k@samsung.com>
Signed-off-by: Wenwen Chen<wenwen.chen@samsung.com>
Link: https://lore.kernel.org/r/20230525082626.577862-1-wenwen.chen@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Wenwen Chen 2023-05-25 16:26:26 +08:00 committed by Jens Axboe
parent 293007b033
commit 533ab73f5b
1 changed files with 5 additions and 1 deletions
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6
io_uring/sqpoll.c
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@ -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;
}