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Date: Sun, 17 Jan 2021 10:16:23 +0000 From: "Zhang, Qiang" <Qiang.Zhang@...driver.com> To: Peter Zijlstra <peterz@...radead.org>, "laijs@...ux.alibaba.com" <laijs@...ux.alibaba.com> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: 回复: Question on workqueue: Manually break affinity on hotplug Hello Peter, Lai Sorry to disturb again, I'm still confused, when the CPU is offline, we active call set_cpus_allowed_ptr function to reset per-cpu kthread cpumask, in sched_cpu_dying function , migrate_tasks function will reset per-cpu kthread's cpumask on runq, even if not on runq, when wake up, other online CPUs will also be selected to run. what I want to ask is why we take the initiative to set it up? Thanks Qiang ________________________________________ 发件人: Peter Zijlstra <peterz@...radead.org> 发送时间: 2021年1月14日 17:11 收件人: Zhang, Qiang 抄送: linux-kernel@...r.kernel.org 主题: Re: Question on workqueue: Manually break affinity on hotplug [Please note this e-mail is from an EXTERNAL e-mail address] On Thu, Jan 14, 2021 at 08:03:23AM +0000, Zhang, Qiang wrote: > Hello Peter > > Excuse me, I have some questions for you, about a description of this change: > > ''Don't rely on the scheduler to force break affinity for us -- it will > stop doing that for per-cpu-kthreads." > > this mean when cpuhotplug, scheduler do not change affinity for per-cpu-kthread's task, if we not active setting affinity? > but if per-cpu-kthread's task is not run state, when wake up, will reset it's affinity, this is done automatically. > > or is it, this place modified to fit the new one hotplug mechanism which > ("sched/hotplug: Consolidate task migration on CPU unplug")? https://lkml.kernel.org/r/20201214155457.3430-1-jiangshanlai@gmail.com https://lkml.kernel.org/r/20201218170919.2950-1-jiangshanlai@gmail.com https://lkml.kernel.org/r/20201226025117.2770-1-jiangshanlai@gmail.com https://lkml.kernel.org/r/20210111152638.2417-1-jiangshanlai@gmail.com https://lkml.kernel.org/r/20210112144344.850850975@infradead.org
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