https://bugs.freedesktop.org/show_bug.cgi?id=97260
Bug ID: 97260 Summary: R9 290 low performance in Linux 4.7 Product: DRI Version: unspecified Hardware: x86-64 (AMD64) OS: Linux (All) Status: NEW Keywords: regression Severity: major Priority: high Component: DRM/Radeon Assignee: dri-devel@lists.freedesktop.org Reporter: magolobel@yahoo.com.br
Starting with Linux Kernel 4.7, the Radeon R9 290 started showing very low performance, about 20/30% of what is available up to kernel 4.6. As can be seen in this article, the performance regression started even before the launch of kernel 4.7 RC1, using Alex Deucher's drm-next-4.7 branch:
http://www.phoronix.com/scan.php?page=article&item=radeon-drm-next-47&am...
Some time later it was speculated that the problem may be with DPM:
http://www.phoronix.com/scan.php?page=news_item&px=Linux-4.7-R9-290-Regr...
To replicate the bug, install Ubuntu 16.04 64bits and install kernel 4.7 from here (preferably above rc5):
http://kernel.ubuntu.com/~kernel-ppa/mainline/
The performance regression will show right away. Rebooting the system and choosing a kernel version up to 4.6 will fix the bug.