From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
tglx@linutronix.de, linux-pm@vger.kernel.org
Subject: Re: [PATCHSET] workqueue: reimplement CPU hotplug to keep idle workers
Date: Fri, 20 Jul 2012 09:52:13 -0700 [thread overview]
Message-ID: <20120720165213.GD32763@google.com> (raw)
In-Reply-To: <1342802391.2583.11.camel@twins>
Hello, Peter.
On Fri, Jul 20, 2012 at 06:39:51PM +0200, Peter Zijlstra wrote:
> On Tue, 2012-07-17 at 10:12 -0700, Tejun Heo wrote:
> > Currently, workqueue destroys all workers for offline CPUs unless
> > there are lingering work items.
>
> _that_ is the root of all ugly in that thing. I still find it utterly
> insane you can create 'per-cpu' workqueues and then violate the per-cpu
> property with hotplug and get your work ran on a different CPU.
Let's talk about this part in the other reply you made.
> It should be a hard error to use queue_work_on() and then run the work
> on a different cpu. Yet somehow this isn't so.
Ooh, yeah, I agree. That's next on the wq to-do list. The problem is
that queue_work() is implemented in terms of queue_work_on(). In most
cases, the local binding serves as locality optimization than anything
else. There are use cases where affinity is required for correctness.
The assumption was that they should flush during CPU_DOWN but it
probably will be much better to require users which need CPU affinity
to always use queue_work_on() - instead of implicit local affinity
from queue_work() - and flush them automatically from wq callback.
Thanks.
--
tejun
next prev parent reply other threads:[~2012-07-20 16:52 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-17 17:12 [PATCHSET] workqueue: reimplement CPU hotplug to keep idle workers Tejun Heo
2012-07-17 17:12 ` [PATCH 1/9] workqueue: perform cpu down operations from low priority cpu_notifier() Tejun Heo
2012-07-20 21:52 ` Paul E. McKenney
2012-07-20 21:58 ` Tejun Heo
2012-07-21 21:36 ` Paul E. McKenney
2012-07-22 16:43 ` [PATCH] workqueue: fix spurious CPU locality WARN from process_one_work() Tejun Heo
2012-07-22 21:23 ` Paul E. McKenney
2012-07-17 17:12 ` [PATCH 2/9] workqueue: drop CPU_DYING notifier operation Tejun Heo
2012-07-17 17:12 ` [PATCH 3/9] workqueue: ROGUE workers are UNBOUND workers Tejun Heo
2012-07-17 17:12 ` [PATCH 4/9] workqueue: use mutex for global_cwq manager exclusion Tejun Heo
2012-07-17 17:12 ` [PATCH 5/9] workqueue: drop @bind from create_worker() Tejun Heo
2012-07-17 17:12 ` [PATCH 6/9] workqueue: reimplement CPU online rebinding to handle idle workers Tejun Heo
2012-07-17 17:12 ` [PATCH 7/9] workqueue: don't butcher idle workers on an offline CPU Tejun Heo
2012-07-17 17:12 ` [PATCH 8/9] workqueue: remove CPU offline trustee Tejun Heo
2012-07-17 17:12 ` [PATCH 9/9] workqueue: simplify CPU hotplug code Tejun Heo
2012-07-17 18:43 ` [PATCHSET] workqueue: reimplement CPU hotplug to keep idle workers Rafael J. Wysocki
2012-07-17 19:40 ` Tejun Heo
2012-07-20 15:48 ` Peter Zijlstra
2012-07-20 17:02 ` Tejun Heo
2012-07-20 17:21 ` Peter Zijlstra
2012-07-20 17:50 ` Tejun Heo
2012-07-20 18:22 ` Peter Zijlstra
2012-07-20 18:34 ` Tejun Heo
2012-07-20 19:44 ` Rafael J. Wysocki
2012-07-20 19:41 ` Tejun Heo
2012-07-21 6:42 ` Shilimkar, Santosh
2012-07-23 8:38 ` Peter De Schrijver
2012-07-20 16:39 ` Peter Zijlstra
2012-07-20 16:52 ` Tejun Heo [this message]
2012-07-20 17:01 ` Peter Zijlstra
2012-07-20 17:08 ` Tejun Heo
2012-07-20 17:19 ` Peter Zijlstra
2012-07-20 17:43 ` Tejun Heo
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