What Do 2021 Linux Kernel Stats Reveal About Development Trends?

In 2021 the Linux kernel incorporated many exciting improvements and new hardware support, yet its total commit count and lines of code were lower than in prior years.

According to Phoronix, by December 31, 2021 the kernel source tree involved roughly 24,300 distinct authors who made 1,060,172 commits across 32.2 million lines of code in more than 74,300 files.

The kernel’s line count continues to grow steadily as new features and hardware support are merged into the mainline.

Commit activity in 2021 dropped to about 73,700, down from 90,200 in 2020, 82,800 in 2019 and 80,100 in 2018, a level not seen since 2013.

Phoronix notes that the decline is partly due to only five major kernel releases in 2021 versus six in earlier years, while additional merge windows generated many smaller commits; the upcoming releases 5.16 and 5.17 are slated for early 2022.

Code churn also slowed: 3.2 million lines were added and 1.3 million removed in 2021, compared with 4.0 million added and 1.5 million removed in 2020.

Linus Torvalds remains the most prolific contributor, with the next top five contributors being David S. Miller, Arnd Bergmann, Christoph Hellwig, Lee Jones, and Jakub Kicinski.

The year saw 4,421 distinct email threads related to kernel commits, a slight decrease from 4,603 in 2020 and 4,383 in 2019.