.42 did not fix the issues I was seeing (constant GPU usage even when idle and generally worse performance). Nvidia-SMI confirms this:
nvidia-smi
Thu Mar 15 08:34:29 2018
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 390.42 Driver Version: 390.42 |
|-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
|===============================+======================+======================|
| 0 GeForce GTX 106... Off | 00000000:01:00.0 On | N/A |
| 0% 42C P8 7W / 120W | 38MiB / 6075MiB | 14% Default |
+-------------------------------+----------------------+----------------------+
+-----------------------------------------------------------------------------+
| Processes: GPU Memory |
| GPU PID Type Process name Usage |
|=============================================================================|
| 0 670 G /usr/lib/xorg-server/Xorg 15MiB |
+-----------------------------------------------------------------------------+
GPU-Util should be 0% and Power should be 5w. Additionally “top” shows “[irq/37-nvidia]” using a constant ~2-4% CPU.