Linux kernel 4.5 released with experimental PowerPlay support

After some deliberation, Linux foreman Linus Torvalds has decided that there will be no eighth release candidate for Linux kernel 4.5, but that it is now time for the stable final version after almost two months. That means the merge window for 4.6 is now open.

The kernel had seven rcs and now has experimental support for AMD’s PowerPlay which should significantly improve the performance of newer Radeon graphics cards such as Tonga and Fiji via the amdgpu open source driver. Modern Radeon cards should now also start in power-saving mode and the clock speed should adapt dynamically. PowerPlay support is not enabled by default, but can be enabled with the “amdgpu.powerplay=1” option.

Also, the scalability of the free space of the Btrfs file system has been improved. The file system better keeps track of which blocks are free and which are in use. The cache that keeps track of free space does so in a different, experimental way in this release, reducing the time it takes to refresh each commit.

Support for GCC’s undefined behavior sanitizer has also been added to the release. The code checks whether there are any undefined behavior in certain actions, even though these actions should not actually be in code. These errors can cause crashes or even security issues. For example, undefined behavior includes dividing by zero or using a non-static variable before it is initialized.

In terms of driver architecture, after five years, ARM is now supported multiplatform, i.e. ARMv6 and ARMv7 for both 32- and 64-bit. The entire list of changes and additions can be found on Kernel Newbies.