linux-kernel - Re: [PATCH 1/4] workqueue: Create low-level unbound workqueues cpumask

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Message-ID: <20140501150114.GD25369@localhost.localdomain>
Date:	Thu, 1 May 2014 17:01:17 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Kevin Hilman <khilman@...aro.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Mike Galbraith <bitbucket@...ine.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH 1/4] workqueue: Create low-level unbound workqueues
 cpumask

On Thu, Apr 24, 2014 at 11:37:16AM -0400, Tejun Heo wrote:
> On Thu, Apr 24, 2014 at 04:37:33PM +0200, Frederic Weisbecker wrote:
> > Create a cpumask that limit the affinity of all unbound workqueues.
> > This cpumask is controlled though a file at the root of the workqueue
> > sysfs directory.
> > 
> > It works on a lower-level than the per WQ_SYSFS workqueues cpumask files
> > such that the effective cpumask applied for a given unbound workqueue is
> > the intersection of /sys/devices/virtual/workqueue/$WORKQUEUE/cpumask and
> > the new /sys/devices/virtual/workqueue/cpumask_unbounds file.
> 
> Let's drop "_unbounds" postfix and name it just "cpumask".  We don't
> apply it to per-cpu workqueues now but that really is an
> implementation detail and later when (and if) we actually distinguish
> per-cpu usages for correctness from for optimization, we may as well
> apply the same cpumask to per-cpu ones too.

Makes sense. But I hope this won't confused too much people. Having
a cpumask file suggests it applies to all of them.

> 
> Another thing with naming is that I didn't anticipate having
> attributes at the top directory so the workqueue directories aren't
> namespaced.  Maybe we want to namespace top level knobs?
> "system_cpumask" maybe?  Any better ideas?

Not sure why you want that. It makes sense on directories grouping
file for different subsystem. But here?

Thanks.
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