Commit 51cd2d2d authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: Process extra works in rescuer on memory pressure 



Make the rescuer process more work on the last pwq when there are no
more to rescue for the whole workqueue to help the regular workers in
case it is a temporary memory pressure relief and to reduce relapse.

Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent e5a30c30

kernel/workqueue.c

+29 −2
Original line number Diff line number Diff line
@@ -3461,9 +3461,36 @@ static bool assign_rescuer_work(struct pool_workqueue *pwq, struct worker *rescu 
	struct work_struct *cursor = &pwq->mayday_cursor;

	struct work_struct *work, *n;



	/* have work items to rescue? */

	if (!pwq->nr_active)

		return false;



	/* need rescue? */

	if (!pwq->nr_active || !need_to_create_worker(pool))

	if (!need_to_create_worker(pool)) {

		/*

		 * The pool has idle workers and doesn't need the rescuer, so it

		 * could simply return false here.

		 *

		 * However, the memory pressure might not be fully relieved.

		 * In PERCPU pool with concurrency enabled, having idle workers

		 * does not necessarily mean memory pressure is gone; it may

		 * simply mean regular workers have woken up, completed their

		 * work, and gone idle again due to concurrency limits.

		 *

		 * In this case, those working workers may later sleep again,

		 * the pool may run out of idle workers, and it will have to

		 * allocate new ones and wait for the timer to send mayday,

		 * causing unnecessary delay - especially if memory pressure

		 * was never resolved throughout.

		 *

		 * Do more work if memory pressure is still on to reduce

		 * relapse, using (pool->flags & POOL_MANAGER_ACTIVE), though

		 * not precisely, unless there are other PWQs needing help.

		 */

		if (!(pool->flags & POOL_MANAGER_ACTIVE) ||

		    !list_empty(&pwq->wq->maydays))

			return false;

	}



	/* search from the start or cursor if available */

	if (list_empty(&cursor->entry))