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

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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: Li Chen <me@linux.beauty>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Li Chen
2026-02-02 22:37:53 +08:00
committed by Jens Axboe
parent 806ae939c4
commit 38aa434ab9
2 changed files with 26 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
io_uring/io-wq.c
View File

@@ -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 {

1
io_uring/io-wq.h
View File

@@ -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);