System Information
Operating system: Arch Linux x86_64 Linux 5.0.3-arch1-1-ARCH
Graphics card: Nvidia GTX 960
CPU: i5-2500k

Blender Version
Broken: 2.79 2c0c1f494dcf makepkg 2018-12-22 14:10

Slow tiles in hybrid CPU+GPU mode

1. Start blender, switch to cycles & GPU compute
2. Open 'system' tab in preferences
3. Set ticks on CPU and GPU in CUDA tab of 'cycles compute device' section
4. Add 3-subdiv icosphere and hit render

All tiles will be rendered except two. You will see this for a while when they render:

Cancelling during this process is also slow.

If you uncheck CPU or GPU in CUDA everything goes well. Also CPU compute works well.

Simple blend used: