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Linux Kernel 6.8 Released, This is What’s New

After several solid months of development the Linux 6.8 kernel has been officially released.

This kernel is of particular note to Ubuntu users as it’s the version chosen to ship in Ubuntu 24.04 LTS – i.e., as the GA kernel and thereby supported for the duration of the release.

Announcing the release of Linux kernel 6.8 on the official Linux Kernel Mailing List (LKML) Linux founder Linus Torvalds says:

“This is not the historically big release that 6.7 was – we seem to be back to a fairly average release size for the last few year.”

Adding: “You can see it in the overall diffstats too – this looks like an average release in pretty much all respects, and we don’t have (for example) any obvious big new filesystems or architectures. I think the biggest single new thing in 6.8 is probably the new Xe drm driver, but honestly, the big bulk of changes are just various random updates and fixes all over.”

So what’s new exactly?

Linux 6.8: New Features
As you’d expect, Linux kernel 6.8 includes plenty of prep, bring-up, and early enablement for hardware and hardware-enabled features most of us aren’t currently using.

This includes the experimental Intel Xe DRM driver Linus mentions in his release announcement, plus further support for AMD Zen 5 and other upcoming AMD hardware, initial code for Qualcomm Snapdragon 8 Gen 3 (and related SoCs), and similar.

But for me, the truly exciting Linux kernel changes are the ones I can feel, benefit from, or make use of myself right now.

And thankfully Linux 6.8 comes with a bunch of them!

Linux 6.8 adds adds Raspberry Pi 5 support to the V3D DRM driver, plus intros GPUTop and FDINFO. Any distro pairing Mesa 23.3 with Linux 6.8 will now provide a solid graphics experience out-of-the-box on the Pi 5, no extra kernel patches required.

This change should ensure Ubuntu 24.04 LTS runs sweet as pie on the Raspberry Pi 5. Turns out Ubuntu already runs sweet as pie as it’s based on the official Raspberry Pi kernel patch set). But this mainline addition is something other Linux distros will benefit from.

As of this kernel reversion the zswap subsystem is now able to force cold pages out to real swap if memory pressure gets too much (with opt-out for those who don’t wish to use this). There’s also a new zswap mode to disable writing back to swap entirely.

Linux kernel 6.8 can prevent direct writes to block devices with mounted filesystems (excepting Btrfs for now). Devs say writing to mounted devices may lead to filesystem corruption and crashes. This feature is disabled by default but it’s reasoned most Linux distros will choose to enable it.

An adjustment to the Intel P-State CPU frequency scaling driver will see devices powered by Intel ‘Meteor Lake’ CPUs (released at the end of last year) hit their advertised ‘boost’ speeds under Linux. In the previous kernel they were found to be running ~100MHz under.

If you use Linux on the Lenovo ThinkPad X1 Carbon (Gen 12), Acer Swift Go 14, ASUS Expertbook B5, or any other laptop powered by Intel Core Ultra Mobile processors expect a pinch more performance during peak loads with this Linux kernel.

On the subject of portables, AMD Ryzen 7000 (and upcoming Ryzen 8000) laptops were suffering from radio frequency interference (RFI) from the Wi-Fi and GPU memory clocks. Linux 6.8 includes AMD RFI mitigations (WBRF) to resolve this.

Network-related: Linux 6.8 includes networking buffs that provide better cache efficiency. This is said to improve “TCP performances with many concurrent connections up to 40%” – a sizeable uplift, though to what degree most users will benefit is unclear.

Are you a Linux gamer? If so, take note that Linux 6.8 gains support for:

Nintendo Switch Online controllers
Powkiddy X5 & RK2023 handheld consoles
Adafruit Mini I2C gamepads
Lenovo Legion Go controllers
Colour management on the Steam Deck
Driver fixes for the official Steam controller are also included.

In addition to the above there are some other choice highlights in Linux 6.8:

New statmount() and listmount() system calls
New deadline servers mechanism
Rust kernel support for LoongArch CPUs
Possible to change the size of tracing sub-buffers
Guest-first memory feature for KVM
KSM advisor for auto-tuning kernel samepage merging subsystem
11% (or so) higher sys call entry performance on IBM Z
New PHY network driver written in Rust
Intel Trust Domain Extensions (TDX) host-side support
Intel IAA compression accelerator
dmesg info on whether 32-bit support is disabled at boot
perf tool now supports data-type profiling
Apple M1 Thunderbolt DART support
Bcachefs gains initial online filesystem check and repair
AppArmor switches to SHA-256 for policy-hash verification
Finally, while few (if any) of us run Linux on RISC-V boards there’s no denying that this open-source processor architecture has a very bright future.

Brighter still as Linux 6.8 works with AMD’s MicroBlaze V soft-core RISC-V CPU; adds XIP kernel features and riscv_hwprobe() system calls; can suspend to RAM on RISC-V when SUSP SBI extension is present; ships a new camera subsystem driver for the StarFive SoC.

For more details on all of the above I (as ever) recommend sifting through the 2-part LWN merge roundups (part 1 & part 2) which offer a concise, waffle-free overview plus links to related in-depth and further info where needed.

Getting Linux kernel 6.8
As for getting Linux 6.8, you can download the source code right now to compile the kernel by hand. Bit much; you’re best off waiting for your Linux distribution to package Linux kernel 6.8 officially and push it out to you as a software update.

Next month you can install or upgrade to Ubuntu 24.04 LTS which includes Linux 6.8 by default (and this will be back ported to Ubuntu 22.04 LTS in the next HWE/ Ubuntu 22.04.5 LTS).

Though other Linux blogs suggest it, using Canonical’s mainline kernel builds is not encouraged (not least because they’re not signed so may fail to boot in certain situations, won’t get security updates, don’t contain certain patches, etc).

That said, some folks do install Canonical mainline kernel builds in Ubuntu (though some only temporarily for testing). If you can’t wait to get your mitts on Linux kernel 6.8 then those pre-packaged DEBs are an option but not an advised one – use ’em at your own risk!”

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