Features You Won't Find With The Mainline Linux 4.15 Kernel

Written by Michael Larabel in Linux Kernel on 28 November 2017 at 06:39 AM EST. 10 Comments
While Linux 4.15 is going to be a mega kernel update with its major new features and changes as we have been covering for the past two weeks, there is some functionality that has yet to see the light of day in mainline.

Among those features that come to mind that remain out of the mainline Linux Git tree include:

BUS1 as the new in-kernel IPC mechanism born out of the failed KDBUS effort. BUS1 remains under development but isn't yet feature complete and ready for mainline. As sort of an interim measure to improve D-Bus in user-space, the BUS1 developers have also been working on D-Bus Broker. Hopefully in 2018 we'll see BUS1 ready for mainline.

WireGuard has been making waves in recent months as the kernel-based next-gen secure network tunnel. It's looking like it may be ready for merging in 2018 to the excitement of many.

Reiser4 continues to be maintained out-of-tree and occasionally picks up new features like the recently mentioned Zstd compression support. But with no major companies using Reiser4, there has been no big push for getting the code reviewed and ready for merging to mainline.

Bcachefs still holds some hope but we haven't heard much about it recently, but this file-system born out of the Bcache block layer caching code should be interesting once mature. But it's not yet ready for mainline.

ZFS deserves an honorable mention for many Linux users wanting to use ZFS more easily on Linux, but currently license incompatibilities prevent that from happening. Last month was the talk by an Oracle/Sun veteran at the OpenZFS conference about how Oracle could make ZFS better for Linux and get it to mainline. Sadly, since that conference it's been reported that speaker was sacked by Oracle.

Nouveau re-clocking improvements remain a big ticket item open-source NVIDIA driver users still desire... Kepler is the most recent NVIDIA GPUs to have decent re-clocking support but it still must be done manually. The GeForce GTX 900/1000 series GPUs still have no proper re-clocking support due to NVIDIA not releasing the needed PMU signed firmware files to control the GPU cooling, etc. So the ball for now is still blocked in NVIDIA's court and there sadly doesn't appear to be any major improvements on the horizon.

Secure Encrypted Virtualization as found on new AMD EPYC CPUs for encrypting the memory of guest VMs landed in Linux 4.15. But that's only the core code while the KVM-side bits for making use of SEV have been postponed to Linux 4.16. At least then we can then enjoy AMD SEV with KVM guests for better security.

KAISER is interesting for better Linux kernel security and reducing KASLR attack vectors. It didn't make it for Linux 4.15 but looks like it might happen for 4.16.

Clang'ing the Linux kernel was a popular topic a few years back while it's lightened up a bit recently: the ability to build the Linux kernel with LLVM/Clang rather than GCC. Most of the work has been merged to the mainline Linux kernel for AArch64 and x86_64, but there still are a few patches unmerged for allowing a stock Clang to build out the stock Linux kernel code-base in the name of better code portability and those preferring Clang and its tooling to GCC.

Anything else you would have liked to see in Linux 4.15? Let us know in the forums.
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Michael Larabel is the principal author of Phoronix.com 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 OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

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