The New Features Of Linux 4.15: AMDGPU DC, RISC-V, EPYC Benefits, VR Improvements
Written by Michael Larabel in Software on 26 November 2017. Page 1 of 3. 12 Comments

The merge window is effectively over for Linux 4.15 with it being the 14th day of the process, although 4.15-rc1 might not end up coming out today due to Linus Torvalds' traveling around the US Thanksgiving holiday. But with Torvalds tending to not approve major last minute additions to new kernels, we don't anticipate any last minute surprises and therefore here is our feature overview of the changes and new features of Linux 4.15. This is arguably the most exciting and feature-packed kernel update ever.

Linux 4.15 is quite a big update. As of writing, when looking at a Git diff short-stat from v4.14 to the current tip, there have been 11,879 files changed this cycle with 580,942 lines of new code and 272,010 lines of deleted code. In comparison, going from v4.13 to v4.14-rc1 saw 400 fewer files changed and a net gain of just 251,211 lines of code versus the net gain this cycle of 308,932 as of writing... From v4.12 to v4.13-rc1 as additional reference saw just 10,000 files changed.

The bulk of the new code addition in Linux 4.15 is due to AMDGPU DC finally having been merged. This new display stack for the AMDGPU DRM driver added more than 130k lines of code this cycle but now allows for Radeon RX Vega display support (and Raven Ridge), HDMI/DP audio for newer GPUs, atomic mode-setting, prep work towards FreeSync, and various other modern display capabilities with DC (formerly "DAL") being the shared code used across AMD's graphics drivers on Linux and Windows.

As of writing, when cloc'ing the kernel Git tree there are 62,246 text files (61,718 unique files) and a total of 3,120,312 blank lines, 3,363,702 lines of comments, and 17,070,691 lines of detected code. In other words, the Linux 4.15 source files are coming in at roughly 23.5 million lines.

Besides the huge addition of AMDGPU DC, other changes to find with Linux 4.15 include:

Graphics / Direct Rendering Manager

- AMDGPU priority scheduling support to benefit the Radeon graphics cards in a Steam VR environment for ensuring sufficient performance with VR headsets on Linux.

- DRM leasing support was also merged for benefiting virtual reality (VR) use-cases on Linux.

- The HTC Vive VR headset will now be treated as a non-desktop device as other Direct Rendering Manager work around improving SteamVR on Linux.

- Intel Coffee Lake graphics are now considered stable and no longer hidden behind a kernel module parameter. Intel has also continued working on their Cannonlake enablement.

- The Intel DRM driver added support for transparent huge-pages and user-defined priority scheduling.

- The open-source NVIDIA (Nouveau) driver adds support for GeForce GTX 1000 "Pascal" temperature monitoring.

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