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Today, Delayed GPU Switching Comes To Linux

Linux Kernel

Published on 03 February 2010 09:59 AM EST
Written by Michael Larabel in Linux Kernel
24 Comments

Two days ago we reported on hybrid graphics coming to Linux in a crude form that allowed switching between graphics processors on notebook computers that utilize dual graphics processors, one that's meant to deliver the best energy efficient performance while the other GPU is for maximizing the graphics performance in demanding environments. Just 24 hours after this kernel patch hit the Internet it already went through four revisions by Red Hat's David Airlie, which delivered better switching and greater notebook compatibility. Since yesterday this patch has already undergone a few more revisions.

The Linux hybrid graphics patch known as "vga_switcheroo" is now on its sixth revision. The fifth iteration of the graphics switcheroo migrated some of the ATPX handling in the xf86-video-ati driver and the sixth does some preparatory work for hooking in Nouveau support so that NVIDIA graphics processors can be switched on and off. The latest version of this patch can be viewed here.

Airlie has also written a second patch that adds delayed GPU switching. Rather than needing to shutdown the X Server, change run-levels, write to /sys/kernel/debug/vgaswitcheroo/switch, and change back, delayed switching makes the process of switching between GPUs a lot easier. This patch still allows immediate graphics switching to a discrete GPU and an integrated graphics processor, but the delayed switching basically postpones the switch until the X.Org Server is restarted. In other words, it's a lot cleaner to integrate that as soon as you log-out and GDM restarts itself, the delayed switch can occur automatically.

Now we just need the Nouveau driver properly hooked in for NVIDIA graphics card support, GDM integration, and then for the kernel patches to be merged into the mainline kernel. Judging by the pace at which Airlie is attacking this hybrid graphics support, perhaps it will be done tomorrow?

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
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