Linux 7.3‑rc1 Arrives: 40.98 Million Lines of Code—But Only a Few Changes Matter

Linus’s comment: “big” kernel

Linus Torvalds said 7.3‑rc1 has no notable new features, only its size. The merged source now totals about 40.98 million lines, a new record. Approximately one‑third of the added code comes from AMD.

Why the kernel grew: AMD DCN6 headers

AMD contributed DCN6 register definitions for the next‑generation display engine. Supporting new GPUs required adding thousands of address and bit definitions to header files, a largely mechanical effort that serves as “future tickets” rather than immediate functionality.

Performance‑focused changes

Zstd decompression optimization

Usama Arif’s patch removes a repeated CPUID check for BMI2 support. Previously each new compression context performed two serializations of the CPUID query; the new code performs the detection once at startup and reuses the result.

crypto_acomp decompression time: –71 %

crypto_acomp compression time: –18 %

MGLRU bug fix

The Multi‑Gen LRU (MGLRU) memory reclamation mechanism receives a long‑awaited fix, making memory reclaim smoother and reducing stutter and frame drops for regular users.

BPF helper extensions

Two new helpers were added: KF_SPINLOCK_SAFE – marks locked BPF calls as safe. __arena – simplifies passing arena pointers into BPF functions.

Beneficiary groups

AMD Zen 6 platforms

Support for the upcoming Zen 6 architecture is added, improving compatibility for next‑generation AMD consumer platforms.

Apple Silicon (M1–M3)

Initial USB4/Thunderbolt support is merged, enhancing networking and external device handling on Linux for Apple silicon.

Steam Controller (2026)

Drivers for the 2026 Steam Controller are merged, providing native support.

Btrfs

Filesystem‑level performance improvements make snapshot‑heavy workflows more stable and faster.

Other notable changes

KVM receives a 45‑patch refactor, strengthening and accelerating virtualization for cloud and container workloads.

A new “failfs” filesystem is added for fault‑injection testing.

Legacy filesystems EFS and FreeVxFS are removed.

AI involvement in kernel development

AI‑assisted debugging and patch generation have become common. In the 7.2 cycle Linus used Gemini to catch an Intel Xe GPU bug; in 7.3 AI‑generated patches and reviews are part of the normal workflow.

Ubuntu 26.10 and the 7.3 kernel

Ubuntu 26.10 originally targeted Linux 7.2, but the accelerated 7.3 release window means the distribution will likely ship with the newer kernel, making 7.3 the default for the upcoming Ubuntu release.

How to try 7.3‑rc1

Install the Mainline kernel PPA (or mainline/ppa) for a one‑click rc1 install.

Clone the source and compile locally:

git clone https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

and build.

Wait for Ubuntu 26.10 (or its HWE update) to provide the kernel automatically.

Conclusion

The “big” label reflects the line count, while the substantive changes are performance‑oriented optimizations and forward‑looking hardware support, alongside a growing role for AI in kernel development.