Epiphany causes high, and perhaps excessive GPU load
I have two Sapphire Nitro R9 Fury graphics cards with fans that normally turn off during low load, such as when browsing the web. However, with Epiphany, I noticed fans would start spinning every now and then, so I looked at GPU load, temps and power consumption on my primary card. Take a look at vddgfx, temp1 and power1 compared to when I'm using Firefox:
Firefox 61 (with OpenGL compositing forced on, it's off by default)
amdgpu-pci-0900
Adapter: PCI adapter
vddgfx: +0.93 V
fan1: 774 RPM
temp1: +67.0°C (crit = +89.0°C, hyst = -273.1°C)
power1: 19.00 W (cap = 260.00 W)
Epiphany 3.28.2
amdgpu-pci-0900
Adapter: PCI adapter
vddgfx: +1.25 V
fan1: 751 RPM
temp1: +76.0°C (crit = +89.0°C, hyst = -273.1°C)
power1: 59.00 W (cap = 260.00 W)
While offloading work to a GPU can be a good thing, this does seem excessive to me. I can imagine this would hurt battery life quite a bit if this was a mobile device.
In this specific test case I had one tab open with a YouTube-video playing, but pretty much any website shows similar result.