From: Yunfeng Ye yeyunfeng@huawei.com
stable inclusion from linux-4.19.167 commit 2e3e4b337f51ab6e532d9f7c2b900a464cc17460
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[ 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 Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- kernel/workqueue.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index c59d02bf186a..4f05c714f99c 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3646,17 +3646,24 @@ 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; }