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workqueue: Kick a worker based on the actual activation of delayed works 

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>
This commit is contained in:
Yunfeng Ye 2020-11-19 14:21:25 +08:00 committed by Tejun Heo
parent 127c501a03
commit 01341fbd0d
1 changed files with 10 additions and 3 deletions
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13
kernel/workqueue.c
View File

@ -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;
}