Linux also runs 82% of smartphones and nine of the top 10 public clouds, the report, compiled by developers Greg Kroah-Hartman and Jonathan Corbet, says. The report is published by the Linux Foundation.
The report has been released roughly annually since 2008 and, if nothing else, illustrates the explosive growth of a system which former Microsoft chief executive Steve Ballmer once described as a "cancer".
The Linux kernel is released every nine to 10 weeks, and more than 12,000 patches are added for each release. Each release represents the work of more than 1600 developers, some of whom work for 200-odd companies. There are also numerous individual contributors.
From 4.8 to 4.13, about 83,000 changesets have been merged from 4319 individuals representing 519 corporations. While the number of developers and changesets per release have grown, the number of companies making contributions has stayed roughly the same.
The report said some of the new features added to the kernel in this development period included:
- The transparent huge page feature now works with file-backed pages as well as program-data pages, leading to more efficient memory use.
- The documentation system was replaced with a new toolchain backed by Sphinx.
- The kernel’s core timer mechanism was replaced with a more efficient implementation.
- The “express data path” mechanism in the networking stack enables high-speed packet processing with user-loaded BPF programs.
- The BBR congestion-control algorithm would improve networking performance in a number of settings.
- Support for Intel’s cache-allocation technology gives better control over performance for both enterprise and real-time workloads.
- The swapping subsystem has greatly improved scalability – which was important now that persistent-memory devices can be used for swapping.
- Support for persistent memory, which may fundamentally change what can be done with computers, has been greatly improved in general.
- The long-awaited statx() system call is now available.
- The BFQ and Kyber block I/O schedulers provide better performance for a wide variety of I/O workloads.
- The new TEE framework facilitates the use of trusted execution environments on ARM processors.
- The in-kernel TLS implementation allows the offloading of encrypted network streams.
While the 4.9 release was the busiest in the history of the project with 16.214 patches, 4.12 set a record for the number of developers involved and also the number of first-time contributors.
The number of days taken for a release is between nine and 10 days; it took 70 days for versions 4.8 to 4.11 and 63 for 4.12 and 4.13.
The last release, 4.13, contained close to 25 million lines of code. By contrast, the initial release in 1991 contained about 10,000 lines.
The number of companies involved in development was 262 in the 4.8 release and that number fell to 225 in 4.13. But the number of developers grew from 1597 (4.8) to 1681 in the 4.13 release.
Another stat released was the top 30 developers from version 2.6.11 in 2005 - the time from which reliable stats are available - to version 4.13; these 30 contributed about 16% of the total changes in the kernel.
As far as corporate contributions go, Intel topped the table with 10,833 changes, about 13.1% of the total. But second in the line of contributors were those with no affiliation who contributed 6819 changes or 8.2% of the total. Another group, whose status was listed as "unknown", contributed 3408 changes (4.1%) while consultants added 2743 changes or 3.3% of the total.
The 28-page report can be downloaded here.