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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 10:43:21 -0700	[thread overview]
Message-ID: <20120720174321.GH32763@google.com> (raw)
In-Reply-To: <1342804767.2583.40.camel@twins>

Hey,

On Fri, Jul 20, 2012 at 07:19:27PM +0200, Peter Zijlstra wrote:
> > Hmmm?  Not really.  We need to keep count of the ones which reqested
> > fixed binding - ie. the ones which explicitly used queue_work_on() -
> > and then flush on wq CPU_DOWN.  Then, we need to audit the current
> > users which are using queue_work{_on}() + explicit FLUSH on CPU_DOWN
> > and convert them.
> 
> No, that's the wrong way about. Just add another WQ_flag, so you can
> tell which work-queues want sane semantics and those mucking about for
> laughs, say WQ_NON_AFFINE.
> 
> Then those with sane semantics (!WQ_NON_AFFINE) get an explicit flush on
> DOWN and don't need to muck about with detaching and re-attaching etc..

Two things - 1. I'd prefer the CPU-affinity requirement to be explicit
at the callsite.  2. To implement it the way you describe, we would
have to implement per-cpu workqueue flush, which is possible but I
don't wanna complicate flush_workqueue() implementation anymore than
it already is.  It's a still a relatively cold exception path.  No
need to complicate the usual path with it.

Thanks.

-- 
tejun

      reply	other threads:[~2012-07-20 17:43 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
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 [this message]

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