The Features You Won't Find In The Linux 4.12 Kernel

While Linux 4.12 has many new features that amount to over one million new lines, 4.12 goes without some features we sure would have loved to see mainlined in time for this next kernel release.

One of the changes I was most looking forward to would have been finally seeing Heterogeneous Memory Management, which has big implications for GPGPU/OpenCL/compute. HMM can be very useful for modern GPUs and other accelerators for mirroring a process' address space and allow memory to be used transparently by any device process. Lead developer Jerome Glisse was trying to get it in for Linux 4.11 and then 4.12, but sadly it didn't make the cut this round... Hopefully we'll see it for Linux 4.13 and also the patches NVIDIA has been baking for Nouveau support.

Followed close behind wanting HMM is another big feature not yet ready for mainline: AMD's DC/DAL code. AMD's big new display stack still hasn't landed for Linux 4.12. I've been anxious to see DC/DAL code mainlined since then it finally allows HDMI/DP audio to be used with newer Radeon graphics cards: very important for HTPCs but even for all of my test PCs I normally just use HDMI/DP audio. But now the lack of DC is even more pressing because AMD Vega and forthcoming Raven Ridge APUs also depend upon DC for display. So while Vega support is in Linux 4.12, it doesn't have any display support due to DC missing. DC is also needed for other modern display features like HDMI 2.0, atomic mode-setting, eventual open-source FreeSync, and more. Hopefully DC is finally ready with Linux 4.13.

On the Nouveau side, the dream remains with seeing good re-clocking support for Maxwell/Pascal in order to get good performance, but that's a tall order that may never be achieved. With Pascal, re-clocking is even more sticky around the signed firmware situation and unless NVIDIA acts, we probably won't be seeing the Nouveau driver supporting re-clocking anytime soon and thus slow performance.

For Linux 4.12 it would have also been fun to see Bcachefs land, but that's still baking. For the dreamers, some also still hold out hope that one day the licenses will jive where we will be able to see ZFS merged into the mainline Linux kernel.

Some of you out there may have also been hoping AMD had some magical Ryzen patches for Linux 4.12, but none of the material merged this cycle referenced Zen/Ryzen improvements.

Overall, Linux 4.12 is going to be an exciting kernel release with many new features albeit there's a handful of items that sadly weren't ready or didn't make the cut. What else would you have wanted to see in Linux 4.12? Let us know in the forums.