Message-ID: <1430195804.3168.19.camel@gmail.com>
Subject: Re: [PATCH 3/3 V8] workqueue: Allow modifying low level unbound
 workqueue cpumask
From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, linux-kernel@vger.kernel.org,
        Christoph Lameter <cl@linux.com>, Kevin Hilman <khilman@linaro.org>,
        Mike Galbraith <bitbucket@online.de>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Frederic Weisbecker <fweisbec@gmail.com>
Date: Tue, 28 Apr 2015 06:36:44 +0200
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On Mon, 2015-04-27 at 23:44 -0400, Tejun Heo wrote:

> > So, we need an API to modify the wq_unbound_cpumask, and I provided
> > this public function.  Otherwise, the other code can't modify it.
> 
> I see.  I don't have too strong an opinion; however, changing the mask
> is a fairly heavy operation.  Are there specific reasons why we don't
> want to follow the nohz config right away?

Isolation is not only applicable to nohz_full.  Many loads are
unsuitable for nohz_full, yet require maximum isolation.

ATM, nohz_full is not dynamic, but hopefully one day will be.  In the
here and now, we can isolate cores from the scheduler on the fly via
cpusets, a prime API user candidate.

	-Mike

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