What’s New in Linux Kernel 6.9? Key Features, Hardware Support, and Performance Boosts

Linux 6.9, the latest official kernel release announced by Linus Torvalds, brings a range of new features and hardware support improvements, with the merge window for version 6.10 opening soon.

New Feature Highlights

Rust language support added for AArch64 (ARM64) architecture, extending system‑programming language use in the kernel.

Enhanced hardware support: Intel FRED mechanism, AMD SNP client support, and dm‑vdo target for inline deduplication, compression, zero‑block elimination, and thin provisioning.

Performance optimizations: support for GCC named address space feature and initial FUSE passthrough support, allowing the kernel to serve files directly from user‑space FUSE servers.

Filesystem improvements: performance and new features for F2FS, exFAT, EXT4, and Btrfs, including block‑device support for F2FS, directory‑sync speedup for exFAT, atomic‑write flag and online resize for EXT4, and zone‑mode fixes for Btrfs.

Hardware Driver Updates

New hardware support for ChromeOS embedded controller, Marvell Octeon PCI endpoint NIC VF, RENESAS FemtoClock3 wireless clock generator, Qualcomm Snapdragon X Elite processor, among others.

AMD and Intel updates: additional IP block support for future AMD hardware, updated Intel Xe GPU driver, and DisplayPort tunnel support added to the Intel i915 driver.

Performance and Security Enhancements

Memory management performance improvements.

perf tool receives multiple new features.

BPF token support added for privileged system daemons such as systemd, enabling delegation of a subset of BPF subsystem functionality.

Initial support for continuous PTE bits on ARM 64‑bit processors, allowing TLB mappings of larger contiguous physical ranges.

Network Enhancements

Support for TCP_NOTSENT_LOWAT, forwarding ICMP error messages in IPSec, and other MPTCP/IPSec improvements.

New network modes: 2.5GE and 5GE Energy Efficient Ethernet (EEE) links, SPP AMSDU support, and wider‑band OFDMA support.

Filesystem Changes

EXT2 deprecated due to lack of 2038‑problem fixes; still usable in 6.9 but discouraged.

Old NTFS implementation removed; NTFS3 is now the default NTFS driver.

Torvalds described Linux 6.9 as a “fairly normal” release, emphasizing a major rewrite of the timer subsystem and the addition of per‑CPU timer wheels, which greatly improve timer performance, especially for networking. He also noted the new BH workqueue support that replaces the old tasklet mechanism.

Regarding arm64 builds, Torvalds said he does not expect to see major issues, but broader testing coverage would make him happier.

Linux 6.9 is a short‑term support branch expected to be maintained for only a few months, with the 6.10 merge window already opened and a release anticipated in late September 2024.