Red Hat, IBM and Novell remain the top contributors to the Linux kernel, an open source project that has grown by 2.7 million lines of code over the past 16 months, according to a report put out by the Linux Foundation.
The report also shows that Linux creator Linus Torvalds has fallen out of the Top 30 individual contributors when accounting only for kernel changes. Torvalds's work in other areas including reviews and signing off on code still make him one of the top contributors to overall kernel development, the report notes.
"Linus remains an active and crucial part of the development process," the report states.
The data was reported in the a paper titled "Linux Kernel Development," which is an update to the first development report put out in April 2008 by the Linux Foundation. The most recent report is authored by Greg Kroah-Hartman from Novell, Jonathan Corbet of LWN.net and Amanda McPherson from The Linux Foundation
Since the last report in 2008, there has been roughly a 10% increase in the number of developers contributing to each kernel release cycle, which come every 2-3 months. In addition, the number of lines of code added to the kernel each day has nearly tripled.
The kernel now has more than 11.5 million lines of code.
Red Hat, Novell and IBM top the chart of companies whose employees contribute the most changes to the kernel. The three companies account for just over 24% of all changes made to the kernel in the past 16 months.
The report notes that since 2005, more than 5,000 individual developers from nearly 500 companies have contributed to the kernel.
The paper examines four years of history from version 2.6.11 through 2.6.30 of the kernel.
The first edition of the report was published in April 2008 and covered data through the 2.6.24 kernel. This most recent report adds data through the 2.6.30 kernel and highlights changes in the past 16 months that show how kernel development is expanding.
Since the April 2008 paper, changes to the kernel have exploded. The numbers include 10,923 lines of code added (a 70% increase), 5,547 lines removed (68% increase) and 2,243 lines changed (32% increase) per day by the development community.
The report notes that the rate of change is larger than any other public software project of any size.
The changes are aggregated within each kernel development cycle, which now averages 81 days.
To keep up with that pace, the individual development community has doubled in the past three years with the 2.6.30 kernel claiming 1,150 developers.
But the report notes that only a relatively small number of them are doing the majority of the work.
"In any given development cycle, approximately 1/3 of the developers involved contribute exactly one patch. Over the past 4.5 years, the top 10 individual developers have contributed almost 12% of the number of changes and the top 30 developers have contributed over 25%."
The report says that companies supporting kernel development do so for a number of reasons and to bring the most benefit to their commercial efforts, including IBM, Intel, SGI and HP on the hardware side; Red Hat, Novell and MontaVista on the operating system side; Sony, Nokia and Samsung from a component perspective; and non-computer industry companies such as Volkswagen (cars) and Quantum Controls (yacht navigation systems) who use Linux as the foundation for other products.
The report concludes that the accelerating rate of change and rise in contributors reflects a "vibrant and active community, constantly causing the evolution of the kernel in response to a number of different environments it is used in."
Those dynamics, the report says, prove that the development process can adapt to higher speeds that the future likely will demand.