linux-kernel - Re: [PATCH wq/for-6.9 v4 2/4] workqueue: Enable unbound cpumask update on ordered workqueues

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Date: Wed, 7 Feb 2024 11:18:24 -1000
From: Tejun Heo <tj@...nel.org>
To: Waiman Long <longman@...hat.com>
Cc: Lai Jiangshan <jiangshanlai@...il.com>, linux-kernel@...r.kernel.org,
	Juri Lelli <juri.lelli@...hat.com>,
	Cestmir Kalina <ckalina@...hat.com>,
	Alex Gladkov <agladkov@...hat.com>, Phil Auld <pauld@...hat.com>,
	Costa Shulyupin <cshulyup@...hat.com>
Subject: Re: [PATCH wq/for-6.9 v4 2/4] workqueue: Enable unbound cpumask
 update on ordered workqueues

Hello, Waiman.

On Wed, Feb 07, 2024 at 03:59:06PM -0500, Waiman Long wrote:
> > But why do we need this? Isn't all that needed to call unplug_oldest during
> > workqueue initialization and chaining unplugging from pwq release from there
> > on?
> 
> Yes, it is possible to just do unplug_oldest_pwq() in pwq_release_workfn()
> and don't do it in apply_wqattrs_cleanup(). As said above, I just want to
> reduce the latency when the old pwq to be retired is idle. I can certainly

They should retire as soon as all the work items are done.

> update the patch to just do it in pwq_release_workfn() if you don't that it
> is necessary to do that too in apply_wqattrs_cleanup(). That will eliminate
> the need for the extra arugment and simplify unplug_oldest_pwq().

So, yeah, let's please keep it simple for now. We can add optimizations
later if this becomes a problem, right?

Thanks.

-- 
tejun