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Subject[PATCH 02/24] workqueue: Cleanups around process_scheduled_works()
Date
* Drop the trivial optimization in worker_thread() where it bypasses calling
process_scheduled_works() if the first work item isn't linked. This is a
mostly pointless micro optimization and gets in the way of improving the
work processing path.

* Consolidate pool->watchdog_ts updates in the two callers into
process_scheduled_works().

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/workqueue.c | 29 +++++++++++------------------
1 file changed, 11 insertions(+), 18 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9a97db94e1dc..c1e56ba4a038 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2634,9 +2634,15 @@ __acquires(&pool->lock)
*/
static void process_scheduled_works(struct worker *worker)
{
- while (!list_empty(&worker->scheduled)) {
- struct work_struct *work = list_first_entry(&worker->scheduled,
- struct work_struct, entry);
+ struct work_struct *work;
+ bool first = true;
+
+ while ((work = list_first_entry_or_null(&worker->scheduled,
+ struct work_struct, entry))) {
+ if (first) {
+ worker->pool->watchdog_ts = jiffies;
+ first = false;
+ }
process_one_work(worker, work);
}
}
@@ -2717,17 +2723,8 @@ static int worker_thread(void *__worker)
list_first_entry(&pool->worklist,
struct work_struct, entry);

- pool->watchdog_ts = jiffies;
-
- if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
- /* optimization path, not strictly necessary */
- process_one_work(worker, work);
- if (unlikely(!list_empty(&worker->scheduled)))
- process_scheduled_works(worker);
- } else {
- move_linked_works(work, &worker->scheduled, NULL);
- process_scheduled_works(worker);
- }
+ move_linked_works(work, &worker->scheduled, NULL);
+ process_scheduled_works(worker);
} while (keep_working(pool));

worker_set_flags(worker, WORKER_PREP);
@@ -2802,7 +2799,6 @@ static int rescuer_thread(void *__rescuer)
struct pool_workqueue, mayday_node);
struct worker_pool *pool = pwq->pool;
struct work_struct *work, *n;
- bool first = true;

__set_current_state(TASK_RUNNING);
list_del_init(&pwq->mayday_node);
@@ -2820,12 +2816,9 @@ static int rescuer_thread(void *__rescuer)
WARN_ON_ONCE(!list_empty(scheduled));
list_for_each_entry_safe(work, n, &pool->worklist, entry) {
if (get_work_pwq(work) == pwq) {
- if (first)
- pool->watchdog_ts = jiffies;
move_linked_works(work, scheduled, &n);
pwq->stats[PWQ_STAT_RESCUED]++;
}
- first = false;
}

if (!list_empty(scheduled)) {
--
2.40.1
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