[PATCH AUTOSEL 5.10 01/17] workqueue: Kick a worker based on the actual activation of delayed works

Sasha Levin
2021-01-05T01:00:14Z

From: Yunfeng Ye <yeyunfeng@huawei.com>

[ Upstream commit 01341fbd0d8d4e717fc1231cdffe00343088ce0b ]

In realtime scenario, We do not want to have interference on the
isolated cpu cores. but when invoking alloc_workqueue() for percpu wq
on the housekeeping cpu, it kick a kworker on the isolated cpu.

alloc_workqueue
pwq_adjust_max_active
wake_up_worker

The comment in pwq_adjust_max_active() said:
"Need to kick a worker after thawed or an unbound wq's
max_active is bumped"

So it is unnecessary to kick a kworker for percpu's wq when invoking
alloc_workqueue(). this patch only kick a worker based on the actual
activation of delayed works.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/workqueue.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 437935e7a1991..0695c7895c892 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3728,17 +3728,24 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
* is updated and visible.
*/
if (!freezable || !workqueue_freezing) {
+ bool kick = false;
+
pwq->max_active = wq->saved_max_active;

while (!list_empty(&pwq->delayed_works) &&
- pwq->nr_active < pwq->max_active)
+ pwq->nr_active < pwq->max_active) {
pwq_activate_first_delayed(pwq);
+ kick = true;
+ }

/*
* Need to kick a worker after thawed or an unbound wq's
- * max_active is bumped. It's a slow path. Do it always.
+ * max_active is bumped. In realtime scenarios, always kicking a
+ * worker will cause interference on the isolated cpu cores, so
+ * let's kick iff work items were activated.
*/
- wake_up_worker(pwq->pool);
+ if (kick)
+ wake_up_worker(pwq->pool);
} else {
pwq->max_active = 0;
}
--
2.27.0