Linux 5.13 To Allow Zstd Compressed Modules, Zstd Update Pending With Faster Performance

Adding to the variety of places where the Linux kernel supports making use of Zstd compression, kernel modules moving forward can now enjoy size reductions with Zstd.

Linux already supports optional Gzip and XZ compression of kernel modules while beginning with Linux 5.13 there is support added for Zstd. In user-space, KMOD 28 already supports dealing with Zstd-compressed modules. The compressed modules are suffixed .ko.zst.

The support for Zstd compressed kernel modules was sent in as part of the Kbuild updates for the Linux 5.13 merge window. The Kbuild updates also include more LLVM Clang compiler handling work and other alterations, including an indicator whether the kernel was built with link-time optimizations (LTO).

Separate from the Kbuild updates and likely for post-5.13, there is renewed work on getting the latest Zstd code within the kernel updated against the upstream state. These patches get the Zstd code in the kernel updated against the latest upstream code, which is much newer than the current Zstd 1.3.1 derived code in the kernel. The Zstd kernel code is now generated automatically from the upstream Zstd code. With this pending Zstd code update for the kernel, Btrfs with Zstd compression is 5~15% faster, SquashFS decompression is ~15% faster, F2FS Zstd is 3~20% faster, kernel Zstd decompression is 35% faster, Zram decompression and read is 30% faster, and initramfs Zstd compression is around 5% faster. Plus there are bug fixes and other improvements in re-basing the kernel's Zstd code-base.