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Date: Mon, 4 Jan 2021 19:58:59 -0500 From: Sasha Levin <sashal@...nel.org> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org Cc: Yunfeng Ye <yeyunfeng@...wei.com>, Lai Jiangshan <jiangshanlai@...il.com>, Tejun Heo <tj@...nel.org>, Sasha Levin <sashal@...nel.org> Subject: [PATCH AUTOSEL 5.10 01/17] workqueue: Kick a worker based on the actual activation of delayed works From: Yunfeng Ye <yeyunfeng@...wei.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@...wei.com> Reviewed-by: Lai Jiangshan <jiangshanlai@...il.com> Signed-off-by: Tejun Heo <tj@...nel.org> Signed-off-by: Sasha Levin <sashal@...nel.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
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