linux-kernel - Re: [PATCHSET] workqueue: reimplement CPU hotplug to keep idle workers

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Message-ID: <20120720194114.GA21218@google.com>
Date:	Fri, 20 Jul 2012 12:41:14 -0700
From:	Tejun Heo <tj@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	tglx@...utronix.de, linux-pm@...r.kernel.org
Subject: Re: [PATCHSET] workqueue: reimplement CPU hotplug to keep idle
 workers

Hello, Rafael.

On Fri, Jul 20, 2012 at 09:44:04PM +0200, Rafael J. Wysocki wrote:
> Well, there are use cases I'm not really familiar with.
> 
> Pretty much the only use case I'm sufficiently familiar with is
> suspend/hibernate where we unplug all of the nonboot CPUs at one point.
> 
> The other use cases, which I don't really think are entirely valid,
> are on some ARM platforms where CPUs are unplugged instead of being put into
> C-states or equivalent (because we don't have a good mechanism for handling
> multiprocessor C-states; there's a set of patches for that waiting for
> the merge window in the Len's tree).  I'm hoping to get rid of those
> use cases in future entirely.

I see, so the highest frequency user would most likely be
suspend/resume - especially with opportunistic approach like the one
used in androids.

Thanks for the explanation.

-- 
tejun
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