The 15 Most Interesting Linux 5.15 Kernel Features From NTFS3 To KSMBD & DAMON

Written by Michael Larabel in Linux Kernel on 31 October 2021 at 01:55 PM EDT. 14 Comments
Back in September at the end of the Linux 5.15 merge window was our Linux 5.15 feature overview but given the time since then and that the Linux 5.15 stable kernel will likely be released this evening, here is a recap of the most interesting changes in this new kernel version.

Linux 5.15 will be released by tonight unless Linus Torvalds decides to be conservative with an additional release candidate, which would push the final release back to next Sunday. In any case, here is a look at the most interesting changes and new features from our perspective with this next kernel:

- The new NTFS "NTFS3" file-system driver is present for this code originally developed by Paragon Software.

- KSMBD was merged as an in-kernel SMB file server that aims to be high performance, support advanced features around RDMA and other areas that can be more easily achieved in kernel-space, and being lighter weight than Samba.

- Many new RDNA2 PCI IDs, likely for an AMD Radeon RDNA2 graphics card refresh.

- Initial support for Intel Xe HP and DG2/Alchemist graphics hardware albeit still a work-in-progress.

- Continued bring-up around Intel Alder Lake with various PCI ID additions and other enablement work.

- AMD Zen 3 APU temperature monitoring is finally in place and also a bit more forward-looking with Yellow Carp / Rembrandt APU temperature monitoring also present in k10temp.

- The Apple M1 IOMMU driver was added among other ongoing work around bringing up mainline support for Apple Silicon with the Linux kernel. For Linux 5.16, more work is on the way.

- ASUS ACPI platform profile support for allowing newer ASUS laptops to allow this performance/thermal preference knob to be controlled.

- The AMD Van Gogh APU audio driver was merged with the Steam Deck being among the hardware to benefit from it.

- The Realtek RTL8188EU WiFi driver was merged for replacing the prior Realtek WiFi driver.

- The PREEMPT_RT locking code was merged as representing a bulk of the previously outstanding real-time patches for the Linux kernel. Great seeing the mainline kernel close to holding all the RT functionality!

- Amazon's DAMON was merged as the data access monitoring framework they have been pursuing for proactive memory reclamation and other purposes.

- The new "process_mrelease" syscall for more quickly freeing memory of dying processes.

- Opt-in L1 data cache flushing on context switching in the name of security, but strictly opt-in by system administrators given the performance implications.

- Added hardening to allow clearing caller-used registers prior to returning from a kernel function, building on the support found compiler-side with GCC 11+.

See our Linux 5.15 feature list for a more comprehensive look at all of the changes in store for this kernel version.

Linux 5.16 will be a very exciting successor with its merge window opening immediately following the v5.15 tagging.
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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

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