I’ve had this issue for the first time ~2 months ago. It was happening on KDE5 desktop on Arch. I thought that it’s problem with their compositor and moved back to KDE 4. It was ok there, it was occuring on XFCE too.
About 2 weeks ago I installed Unity on Arch, since then I have same issue as with KDE 5. Performance of TF2 drops from 80-120 fps to 17-30.
I did some tests and I saw one thing happening everytime something pulls handbrake on my GPU.
“PCIe Bandwidth Utilization” when minimized TF2 is in main menu is normally at ~17%, when problem occurs it’s at ~30%.
When I’m in MP on map pl_frontier_final minimized, bandwidth is around 1%, when problem occurs it’s ~56%.
Also, VRAM usage is up to 100MB higher when it occurs.
One last thing, when I leave game, I can’t logout with logout button, only “killall -u user” works. If I switch tty to for example 2 and back to 7 compiz crashes.
ASUS GTX 550 Ti 1GB
Core i3 2100
8GB DDR3 @ 1333 MHz