Getting a lot of these in my dmesg:

[154272.660917] radeon_gem_object_create:62 alloc size 340Mb bigger than 256Mb
limit
[154272.660925] radeon_gem_object_create:62 alloc size 340Mb bigger than 256Mb
limit
[154272.661012] radeon_gem_object_create:62 alloc size 340Mb bigger than 256Mb
limit
[154272.661020] radeon_gem_object_create:62 alloc size 340Mb bigger than 256Mb
limit

They match the similar errors I'm getting from (modded) Minecraft:

[16:08:10] [Client thread/ERROR]: ########## GL ERROR ##########
[16:08:10] [Client thread/ERROR]: @ Post render
[16:08:10] [Client thread/ERROR]: 1285: Out of memory
[16:08:10] [Client thread/ERROR]: ########## GL ERROR ##########
[16:08:10] [Client thread/ERROR]: @ Post render
[16:08:10] [Client thread/ERROR]: 1285: Out of memory
[16:08:10] [Client thread/ERROR]: ########## GL ERROR ##########
[16:08:10] [Client thread/ERROR]: @ Post render
[16:08:10] [Client thread/ERROR]: 1285: Out of memory
[16:08:10] [Client thread/ERROR]: ########## GL ERROR ##########
[16:08:10] [Client thread/ERROR]: @ Post render
[16:08:10] [Client thread/ERROR]: 1285: Out of memory

I'm on Debian Jessie, but I should be able to figure out how to run a newer X
or kernel for testing, if needed.