Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | [PATCH v6 3/4] workqueue: Convert the idle_timer to a timer + work_struct | Date | Mon, 28 Nov 2022 18:31:08 +0000 |
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A later patch will require a sleepable context in the idle worker timeout function. Converting worker_pool.idle_timer to a delayed_work gives us just that, however this would imply turning all idle_timer expiries into scheduler events (waking up a worker to handle the dwork).
Instead, implement a "custom dwork" where the timer callback does some extra checks before queuing the associated work.
No change in functionality intended.
Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- kernel/workqueue.c | 51 +++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 48 insertions(+), 3 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 8185a42848c50..c8b1466a9c070 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -169,7 +169,9 @@ struct worker_pool { struct list_head idle_list; /* L: list of idle workers */ struct timer_list idle_timer; /* L: worker idle timeout */ - struct timer_list mayday_timer; /* L: SOS timer for workers */ + struct work_struct idle_cull_work; /* L: worker idle cleanup */ + + struct timer_list mayday_timer; /* L: SOS timer for workers */ /* a workers is either on busy_hash or idle_list, or the manager */ DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER); @@ -1806,7 +1808,9 @@ static void worker_enter_idle(struct worker *worker) /* idle_list is LIFO */ list_add(&worker->entry, &pool->idle_list); - if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) + if (too_many_workers(pool) && + !timer_pending(&pool->idle_timer) && + !work_pending(&pool->idle_cull_work)) mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); /* Sanity check nr_running. */ @@ -2019,17 +2023,56 @@ static void destroy_worker(struct worker *worker) wake_up_process(worker->task); } +/* + * idle_worker_timeout - check if some idle workers can now be deleted. + * + * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in + * worker_leave_idle(), as a worker flicking between idle and active while its + * pool is at the too_many_workers() tipping point would cause too much timer + * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let + * it expire and re-evaluate things from there. + */ static void idle_worker_timeout(struct timer_list *t) { struct worker_pool *pool = from_timer(pool, t, idle_timer); + bool do_cull = false; + + if (work_pending(&pool->idle_cull_work)) + return; raw_spin_lock_irq(&pool->lock); - while (too_many_workers(pool)) { + if (too_many_workers(pool)) { struct worker *worker; unsigned long expires; /* idle_list is kept in LIFO order, check the last one */ + worker = list_entry(pool->idle_list.prev, struct worker, entry); + expires = worker->last_active + IDLE_WORKER_TIMEOUT; + do_cull = !time_before(jiffies, expires); + + if (!do_cull) + mod_timer(&pool->idle_timer, expires); + } + raw_spin_unlock_irq(&pool->lock); + + if (do_cull) + queue_work(system_unbound_wq, &pool->idle_cull_work); +} + +/* + * idle_cull_fn - cull workers that have been idle for too long. + */ +static void idle_cull_fn(struct work_struct *work) +{ + struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work); + + raw_spin_lock_irq(&pool->lock); + + while (too_many_workers(pool)) { + struct worker *worker; + unsigned long expires; + worker = list_entry(pool->idle_list.prev, struct worker, entry); expires = worker->last_active + IDLE_WORKER_TIMEOUT; @@ -3479,6 +3522,7 @@ static int init_worker_pool(struct worker_pool *pool) hash_init(pool->busy_hash); timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE); + INIT_WORK(&pool->idle_cull_work, idle_cull_fn); timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0); @@ -3626,6 +3670,7 @@ static void put_unbound_pool(struct worker_pool *pool) /* shut down the timers */ del_timer_sync(&pool->idle_timer); + cancel_work_sync(&pool->idle_cull_work); del_timer_sync(&pool->mayday_timer); /* RCU protected to allow dereferences from get_work_pool() */ -- 2.31.1
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