From: Tejun Heo <tj@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Christoph Lameter <cl@linux.com>,
Kevin Hilman <khilman@linaro.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
Mike Galbraith <bitbucket@online.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Viresh Kumar <viresh.kumar@linaro.org>
Subject: Re: [PATCH 4/4] workqueue: Handle ordered workqueues on cpumask_unbounds change
Date: Thu, 24 Apr 2014 11:33:20 -0400 [thread overview]
Message-ID: <20140424153320.GF14460@htj.dyndns.org> (raw)
In-Reply-To: <1398350256-7834-5-git-send-email-fweisbec@gmail.com>
On Thu, Apr 24, 2014 at 04:37:36PM +0200, Frederic Weisbecker wrote:
> Ordered unbound workqueues need some special care if we want to
> modify their CPU affinity. These can't be simply handled through
> apply_workqueue_attrs() since it works by hot plugging worker pools
> which has parallelism side effects and this would break ordering.
>
> The way we solve this is to change the affinity of the (presumaly
> unique) worker backing the ordered workqueues.
>
> NOTE: Now like Lai said, there may be bad side effects on this because
> ordered wq may share their worker pool with non-ordered workqueues.
> So changing the affinity of the worker itself is not a nice solution.
> This patch is very likely to be replaced by Lai's patch
> "workqueue: allow changing attributions of ordered workqueue"
> https://lkml.org/lkml/2014/4/15/181
Yeah, it bothers me that we're taking two completely different
approaches for ordered and !ordered workqueues. The only difference
between them is concurrency and it probably would be a better idea to
address that directly.
Thanks.
--
tejun
next prev parent reply other threads:[~2014-04-24 15:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-24 14:37 [RFC PATCH 0/4] workqueue: Introduce low-level unbound wq sysfs cpumask Frederic Weisbecker
2014-04-24 14:37 ` [PATCH 1/4] workqueue: Create low-level unbound workqueues cpumask Frederic Weisbecker
2014-04-24 15:37 ` Tejun Heo
2014-05-01 15:01 ` Frederic Weisbecker
2014-05-01 15:02 ` Tejun Heo
2014-05-01 15:09 ` Frederic Weisbecker
2014-05-01 15:13 ` Tejun Heo
2014-04-24 22:42 ` Kevin Hilman
2014-04-24 14:37 ` [PATCH 2/4] workqueue: Split apply attrs code from its locking Frederic Weisbecker
2014-04-24 14:48 ` Tejun Heo
2014-05-01 14:40 ` Frederic Weisbecker
2014-05-01 14:41 ` Tejun Heo
2014-04-24 14:37 ` [PATCH 3/4] workqueue: Allow modifying low level unbound workqueue cpumask Frederic Weisbecker
2014-04-24 15:30 ` Tejun Heo
2014-05-01 14:49 ` Frederic Weisbecker
2014-04-24 14:37 ` [PATCH 4/4] workqueue: Handle ordered workqueues on cpumask_unbounds change Frederic Weisbecker
2014-04-24 15:33 ` Tejun Heo [this message]
2014-05-01 14:51 ` Frederic Weisbecker
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