The Linux 6.15 kernel arrives – and it's big a victory for Rust fans

Linus Torvalds officially announced the stable release of the Linux kernel 6.15 on May 25, 2025. Its arrival was delayed for a few hours, Torvalds said, “because of a last-minute bug report resulting in one new feature being disabled at the eleventh hour,” but Linux 6.15 is here and ready for you to download and tinker with. 

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The newest feature that caught my eye was that, for the first time, we have a Rust-based driver in the mainline kernel. Linux Rust fans have been waiting for this development for a long time. 

Oh, and by the way, this is not just “another driver”. The Direct Rendering Manager (DRM) driver, named NOVA, empowers Nvidia’s next-generation open-source graphics hardware. The driver targets Nvidia’s RTX 2000 “Turing” series and newer GPUs. NOVA aims to replace the existing third-party open-source Nouveau Nvidia drivers.

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This development marks the final victory for Linux and open-source software over Nvidia’s old proprietary ways. A dozen years ago, Torvalds famously called out Nvidia as one “of the worst trouble spots we’ve had with hardware manufacturers, and that is really sad because then Nvidia tries to sell chips — a lot of chips — into the Android market.”

Since then, Nvidia figured out they could make a lot more money working with Linux instead of fighting it. Now, with the AI industry living and dying on Nvidia chips running Linux, the tech giant has embraced both the memory-safe Rust language and open source. We can expect to see a lot more Rust-based kernel components soon.

Linux 6.15 also delivers exceptional performance improvements, especially for file operations. The exFAT file system, which is commonly used in USB flash drives and SD cards, now benefits from optimized cluster-discarding algorithms. This shift has led to some truly impressive performance boosts. For example, in Linux, according to journalist Michael Larabel, you can delete an 80GB test file in just 1.6 seconds rather than over four minutes in previous versions. Technically, this feat is achieved by batching contiguous cluster discards rather than deleting clusters individually.

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The Btrfs file system, which is being adopted in Linux distros such as openSUSE and Fedora, also comes with major updates, including support for faster zstd, a lossless compression algorithm, compression levels, and improved direct I/O handling. Files requiring checksums now fall back to buffered writes when needed, reducing errors in virtual machine environments.

Networking improvements include a new zero-copy receive (zcrx) mechanism via io_uring, allowing network packet data to move directly into userspace RAM, and a new TCP socket option for finer control over IPv4 retry timeouts. 

Memory management has been enhanced with a new “dmem” memory accounting cgroup for better tracking of device memory usage and a defrag_mode sysctl to help avoid fragmentation, particularly useful for workloads relying on huge pages.

Linux 6.15 expands hardware support with dedicated drivers for the Apple Touch Bar, a new Samsung Galaxy Book driver for ACPI platform profiles, and battery management. Yes, I know Apple hasn’t been shipping the Touch Bar for years now, but there’s a passionate community of 2016–2020 MacBook Pro users who still love it. 

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I have some bad news, though, for people who still love their 486-based PCs. Linux 6.15 officially drops support for x86 CPUs before Intel Pentium, marking the end for 486-class chips. 

However, Linux still supports some 32-bit Linux hardware, such as 1995’s Pentium Pro. I wouldn’t count on seeing 32-bit Linux support for much longer. If you use archaic hardware, you can still run older Linux kernels. If you want something more up-to-date, there’s always NetBSD/i386, which even continues to support 386 CPUs. 

For newer hardware, the 6.15 kernel has improved support for Apple M1 and Nvidia GPUs. The release also introduces hardware-wrapped inline encryption keys in the block layer for transparent disk encryption with less software overhead.

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The release marks a busy time for Linux kernel developers. Altogether, there were 14,612 changesets. That makes it the “busiest” release since kernel 6.7 at the beginning of 2024. 

Looking ahead, more kernel changes are already on their way. As Torvalds wrote: “It’s Memorial Day tomorrow here in the US, but like the USPS, ‘neither snow nor rain nor heat nor gloom of night’ nor Memorial Day stops the merge window.” Well, he admitted, maybe “sometimes snow *does* stop the merge window. But only temporarily.”