The Exciting Features Of The Linux 4.9 Kernel

Written by Michael Larabel in Software on 17 October 2016 at 11:20 AM EDT.

This weekend was the release of Linux 4.9-rc1 to mark the end of the 4.9 kernel merge window. As such, here's our usual feature overview recapping all of the changes to Linux 4.9 that have us excited about the next version of this open-source kernel.

Some of the highlights include AMDGPU GCN 1.0 experimental support, memory protection keys support, mainline support for the LG Nexus 5 and Raspberry Pi Zero (along with a lot of other ARM hardware), the Greybus subsystem was added, support for vmapped stacks, and many other additions.


- Virtual display support for AMDGPU, better AMDGPU GPU reset support, and other changes for this modern AMD GCN driver.

- AMDGPU also has experimental Southern Islands support (GCN 1.0) as an alternative to the existing support in Radeon DRM. Similar to GCN 1.1, the GCN 1.0 AMDGPU support needs to be manually enabled at compile-time while blacklisting (or disabling) the Radeon DRM driver from loading.

- Various fixes and improvements to the Intel DRM with one of the notable changes being DMA-BUF implicit fencing.

- GPU and memory overhead reduction for the Raspberry Pi VC4 driver during 3D rendering.

- Sadly, no Nouveau (open-source NVIDIA) driver changes were included for Linux 4.9... Leaving out the recent "boost" patches and more.

- Various other DRM changes for Linux 4.9. That's Direct Rendering Manager for those new to Linux that are thinking of the other DRM...

Processors / Memory:

- A P-State change that can boost performance for some Intel Atom CPUs.

- CPUFreq continues making greater use of scheduler information.

- Memory protection keys support. This MPK / Pkeys support is finally in the mainline kernel for the new instructions to be supported by future Intel CPUs.

- Various Xen and KVM changes for the Linux virtualization stack.

- Support for vmapped kernel stacks as one of the changes that excite Linus Torvalds the most.

File-Systems / Storage:

- UBIFS support for OverlayFS while UBI gets ready for MLC NAND support.

- Shared data extents for XFS.

- Fixes for Btrfs.

- NVDIMM support updates.

- Various XFS updates.

- F2FS performance enhancements.

- MD RAID improvements.

- FUSE support for POSIX ACLs.

- OverlayFS SELinux support.

Other Hardware:

- Support for 29 more ARM machines, including the Raspberry Pi Zero, LG Nexus 5, and other notable mobile/embedded hardware.

- Intel Integrated Sensor Hub (ISH) support.

- New Elan touchscreen driver and GPIO decoder.

- Continued Skylake audio work via the sound updates for Linux 4.9.

- Mellanox platform support.

- The EFI test driver is now mainline thanks to Canonical.

General Work:

- Kthread improvements.

- Various perf updates.

- An assortment of scheduler changes.

- The Greybus subsystem was added to the staging area. Greybus was crucial to Google's failed Project Ara modular smartphone but will still be used in future devices.

That's a lot of stuff coming for Linux 4.9! Expect Linux 4.9 to be officially released in mid-to-late December. Stay tuned for more Linux 4.9 kernel coverage, particularly many hardware benchmarks and of changes in this upgraded kernel, in future Phoronix articles. If you appreciate my single-handed coverage here of all the happenings and plenty of benchmarks along with the automated efforts like daily benchmarks of the Linux kernel at, consider joining Phoronix Premium.

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Michael Larabel

Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via