linux-kernel - Thunderbolt, Apple Monitor & MBA, and excess kworker load

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Date:	Wed, 20 Jun 2012 17:48:42 +0200
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	daniel.vetter@...ll.ch, dri-devel@...ts.freedesktop.org,
	gregkh@...uxfoundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: Thunderbolt, Apple Monitor & MBA, and excess kworker load

Hi,

At work, I wish to attach a 27" Apple Display using thunderbolt to my Mac
Book Air 4,2 13". Using OS X, it works fine, but as I prefer using Linux, I
tested out Ubuntu's stock kernel and (among other) 3.5.0-rc3+ as of f40759e.
Hotplug doesn't work (known issue), but also with coldplug the display
reacts _very_ slow, way too slow for real use: The screen updates only every
half second or so. Is this a known bug? Might something go afoul with
kworker -- they need about 75% of the CPU with the large display attached,
and less than 1% _without_ the large display.

Any hints are most welcome, also on where I may dig further to determine the
root causes...

Thanks & best,

	Dominik
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