I get random lagging when playing the recently released Mad Max. Every once in
a while, the game freezes completely, and gets back to the game after an
arbitrary amount of seconds, anywhere from 2 to 35. 

With GALLIUM_HUD, and noticed that the lags appear to precede the VRAM slowly
ramping up to full, and then I get this huge lag, and then VRAM usage is a lot
lower (eg. from 1GB to ~600MB).

I found this possibly related news item from a couple of months back:
https://www.gamingonlinux.com/articles/a-reason-for-poor-performance-on-amd-plus-mesa-has-been-found-and-a-patch-is-in-progress.7873