Commit 38aa434a authored by Li Chen's avatar Li Chen Committed by Jens Axboe
Browse files

io_uring/io-wq: add exit-on-idle state 



io-wq uses an idle timeout to shrink the pool, but keeps the last worker
around indefinitely to avoid churn.

For tasks that used io_uring for file I/O and then stop using io_uring,
this can leave an iou-wrk-* thread behind even after all io_uring
instances are gone. This is unnecessary overhead and also gets in the
way of process checkpoint/restore.

Add an exit-on-idle state that makes all io-wq workers exit as soon as
they become idle, and provide io_wq_set_exit_on_idle() to toggle it.

Signed-off-by: default avatarLi Chen <me@linux.beauty>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 806ae939

io_uring/io-wq.c

+25 −2
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ enum { 


enum {

	IO_WQ_BIT_EXIT		= 0,	/* wq exiting */

	IO_WQ_BIT_EXIT_ON_IDLE	= 1,	/* allow all workers to exit on idle */

};



enum {
@@ -707,9 +708,13 @@ static int io_wq_worker(void *data) 
		raw_spin_lock(&acct->workers_lock);

		/*

		 * Last sleep timed out. Exit if we're not the last worker,

		 * or if someone modified our affinity.

		 * or if someone modified our affinity. If wq is marked

		 * idle-exit, drop the worker as well. This is used to avoid

		 * keeping io-wq workers around for tasks that no longer have

		 * any active io_uring instances.

		 */

		if (last_timeout && (exit_mask || acct->nr_workers > 1)) {

		if ((last_timeout && (exit_mask || acct->nr_workers > 1)) ||

		    test_bit(IO_WQ_BIT_EXIT_ON_IDLE, &wq->state)) {

			acct->nr_workers--;

			raw_spin_unlock(&acct->workers_lock);

			__set_current_state(TASK_RUNNING);
@@ -967,6 +972,24 @@ static bool io_wq_worker_wake(struct io_worker *worker, void *data) 
	return false;

}



void io_wq_set_exit_on_idle(struct io_wq *wq, bool enable)

{

	if (!wq->task)

		return;



	if (!enable) {

		clear_bit(IO_WQ_BIT_EXIT_ON_IDLE, &wq->state);

		return;

	}



	if (test_and_set_bit(IO_WQ_BIT_EXIT_ON_IDLE, &wq->state))

		return;



	rcu_read_lock();

	io_wq_for_each_worker(wq, io_wq_worker_wake, NULL);

	rcu_read_unlock();

}



static void io_run_cancel(struct io_wq_work *work, struct io_wq *wq)

{

	do {

io_uring/io-wq.h

+1 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ struct io_wq_data { 
struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data);

void io_wq_exit_start(struct io_wq *wq);

void io_wq_put_and_exit(struct io_wq *wq);

void io_wq_set_exit_on_idle(struct io_wq *wq, bool enable);



void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work);

void io_wq_hash_work(struct io_wq_work *work, void *val);