I think the general slowness, even when not doing anything, is caused by cpu load, not GPU load.
Text rendering seems slow, when testing it in the researchtree, zoom out till text is gone ; fps rises , zoom slightly back in till text appears ; 75% fps hit from 50 to 10 fps
All the while the Graphics GPU performance meter in radeontop never goed above 50%
When I strace the game and am at the opening screen menu doing nothing (but also anywhere else in the game), I get a constant stream of this;
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11321, NULL) = -1 EAGAIN (Resource temporarily unavailable)
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
ioctl(8, 0x40086464, 0x7ffcfe469d90) = 0
ioctl(8, 0xc008646a, 0x7ffcfe469cc0) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11323, NULL) = -1 EAGAIN (Resource temporarily unavailable)
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
ioctl(8, 0x40086464, 0x7ffcfe469d90) = 0
ioctl(8, 0xc008646a, 0x7ffcfe469cc0) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11325, NULL) = -1 EAGAIN (Resource temporarily unavailable)
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
ioctl(8, 0x40086464, 0x7ffcfe469d90) = 0
ioctl(8, 0xc008646a, 0x7ffcfe469cc0) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11327, NULL) = -1 EAGAIN (Resource temporarily unavailable)
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
ioctl(8, 0x40086464, 0x7ffcfe469d90) = 0
ioctl(8, 0xc008646a, 0x7ffcfe469cc0) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11329, NULL) = -1 EAGAIN (Resource temporarily unavailable)
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
ioctl(8, 0x40086464, 0x7ffcfe469d90) = 0
ioctl(8, 0xc008646a, 0x7ffcfe469dc0) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11331, NULL) = 0
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
ioctl(8, 0x40086464, 0x7ffcfe469e90) = 0
ioctl(8, 0x40086464, 0x7ffcfe46b150) = 0
ioctl(8, 0xc008646a, 0x7ffcfe46b050) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11333, NULL) = 0
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
poll([{fd=6, events=POLLIN|POLLOUT}], 1, 4294967295) = 1 ([{fd=6, revents=POLLOUT}])
writev(6, [{"\223\1\22\0\24\0\200\1\35\0\200\1\316\2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 72}], 1) = 72
recvmsg(6, 0x7ffcfe46afb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
select(7, [6], NULL, NULL, {0, 0}) = 0 (Timeout)
poll([{fd=6, events=POLLIN}], 1, 4294967295) = 1 ([{fd=6, revents=POLLIN}])
recvmsg(6, {msg_name(0)=NULL, msg_iov(1)=[{"#\223\335\3\0\0\0\0\2\0\0\0\27\0\200\1\24\0\200\1\316\2\0\0\35\0\200\1\36\0\200\1"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 72
ioctl(8, 0xc008646a, 0x7ffcfe46abd0) = 0
ioctl(8, 0xc008646a, 0x7ffcfe46abd0) = 0
ioctl(8, 0xc008646a, 0x7ffcfe46abd0) = 0
ioctl(8, 0xc008646a, 0x7ffcfe469c10) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11335, NULL) = -1 EAGAIN (Resource temporarily unavailable)
futex(0xc45e40, FUTEX_WAKE_PRIVATE, 1) = 0
ioctl(8, 0x40086464, 0x7ffcfe469ce0) = 0
ioctl(8, 0xc008646a, 0x7ffcfe469cc0) = 0
futex(0xbaf864, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xbaf860, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
futex(0xbaf838, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0xc45e6c, FUTEX_WAIT_PRIVATE, 11337, NULL) = -1 EAGAIN (Resource temporarily unavailable)