Hybrid Graphics and Ubuntu 14.04's gpu-manager?

[Guest]

I'm wondering if there's any documentation or if anyone knows as to how exactly Ubuntu 14.04's gpu-manager works when handling which GPU to use?

I use a dual-AMD GPU muxless laptop (iGPU is on the APU + discrete GPU; 7660G + 7670M). After installing fglrx and doing the initial xorg.conf configuration, I reboot. Upon rebooting though, the gpu-manager (according to the log) removes the customized xorg.conf, and replaces it with it's own.

Both of my GPUs are still detected (in gpu-manger's log, xorg's log, CCC shows a ghost card of the dGPU under monitor settings, and amdconfig --lsa shows both cards), but fglrxinfo only shows info for the iGPU.

I haven't tried any games yet, but I'm curious as to how said games will interact with the dGPU, and if there's any way to prove such. Will both cards just work together perfectly? What about power savings? Will the dGPU not be used on battery? Also what about amdconfig-specific settings, such as --tls (nothing can be set since xorg.conf is wiped on reboot)?

I've tried amdconfig --odgc --adapter=1 (for the dGPU), and it failed (I generated the custom xorg.conf and tried without reboot; otherwise, it would tell me to run initial config). It works fine for adapter 0 (iGPU) though.

[Guest]

Dota 2 as-is with the latest fglrx-updates and Ubuntu's gpu-manager had extremely low FPS (9-12 FPS). I'm assuming it wasn't using the dGPU at all, but that framerate even seemed low for just the iGPU being used, if I recall right anyway.

Removing ubuntu-drivers-common allowed for customization of xorg.conf again, and after doing that, Dota 2's framerate was between 20-50 (erratic, but better) on the dGPU.

So it would seem gpu-manager either needs some kind of user-intervention to work properly, it's incomplete (maybe the more likely reason; 14.04 isn't released yet), or just plainly doesn't work.