Apple Thunderbolt Display Presents Problems For Linux

While waiting for the Apple Thunderbolt Display order to arrive, I wasn't too sure what to expect. Back in May there was word that the Thunderbolt Linux support wasn't all lined up. Recently via Twitter I heard from a Phoronix reader that the Apple Thunderbolt Display works under Linux, but there are a few issues -- including very high CPU usage.

After connecting the Thunderbolt display to the Apple Mac Mini with its Intel Sandy Bridge processor and integrated graphics, along with trying out the USB and Ethernet ports, a development snapshot of Ubuntu 12.10 with the Linux 3.5 kernel was tested to experience the very latest Linux code. To some surprise, when booting Ubuntu Linux on the Apple Mac Mini, the display lit up! Mode-setting via the Intel DRM/KMS driver also happened correctly to 2560 x 1440 without needing any manual configuration options. Beyond that, the Broadcom Gigabit Ethernet over Thunderbolt properly worked, the Pericom USB controller over Thunderbolt properly worked, and the LSI Firewire controller also worked from the display.

At first this looked very successful seeing not only the display lighting up when running Ubuntu 12.10 and the connectivity working, but also when beginning to trying to interact with the system was when realizing there was problems. Trying to interact with the Linux desktop was very sluggish: the mouse cursor was slow to respond, menus were slow, and everything was just very slow. When looking at the CPU usage, as I first learned from Twitter, the CPU was being eaten alive. Idling at the desktop of Ubuntu 12.10 with no extra processes active was now keeping one of the Sandy Bridge CPU cores generally close to 100% busy. When engaging in any task, the CPU load was now much greater than when not using a Thunderbolt display. While it was sluggish to test, the FaceTime HD camera had also functioned correctly.