| Linux kernel developers increase by 10 percent |
Aug. 20, 2009
 The Linux Foundation has published an update to last year's study on Linux kernel development. The updated study reports that for each kernel release there has been a 10 percent increase in the number of contributing developers, resulting in a 42 percent increase in patch acceptance.
Written by original authors and kernel developers Jonathan Corbet and Greg Kroah-Hartman, as well as the Linux Foundation's VP of marketing Amanda McPherson, "Who Writes Linux?" updates the April 2008 study, "Linux Kernel Development: How Fast is it Going, Who is doing it and Who is Sponsoring it?" The new statistics build upon the original study, which revealed that the number of Linux kernel developers has tripled since 2005, with many more companies contributing to the process. The update has been issued a week after the latest Linux 2.6.31-rc6 kernel maintenance release was announced by Linus Torvalds (see more farther below).
With the number of kernel developers growing by 10 percent since April 2008, some 2.7 million lines of code have been added to the kernel, reports the Linux Foundation (LF) report. The rate of patch acceptance, meanwhile, is said to have increased by a whopping 42 percent since that time, resulting in 5.45 patches being accepted per hour. This is due not only to the new kernel contributors, but by "new demand for Linux in emerging markets, such as netbooks, auto, and energy," says the report.
The report also links the accelerated development to the establishment of the new "Linux-next" tree staging area. Linux-next helps to accelerate development of the subsequent kernel cycle while development is still underway on the current release.
Number of developers per Linux kernel release (Source: Linux Foundation)
(Click to enlarge)
In the updated study, LWN.net editor Corbet and Novell fellow Kroah-Hartman, who are members of the Linux Foundation's Technical Advisory Board (TAB), reviewed the last six kernel releases, from 2.6.24 through 2.6.30. In focusing on these 500 days of Linux development, the report reveals how the Linux development process works, including who is contributing, how often, and why, says the LF.
Development days per Linux kernel release (Source: Linux Foundation)
(Click to enlarge)
Findings in the report are said to include:- Every Linux kernel is being developed by nearly 1,000 developers, working for more than 200 different corporations, making Linux the largest distributed software development project in the world.
- Since 2008, the number of individual developers has increased by 10 percent.
- More than 70 percent of total contributions originate from developers working at technology companies, which are said to believe that participation in kernel development give them a competitive edge.
- The top five companies with developers participating in the Linux kernel development process are said to be Red Hat, Google, Novell, Intel, and IBM.
- A net of 2.7 million lines of code have been added since April 2008, with 10,923 lines of code added every day, representing a faster change rate than any other public software project.
- An average of 5,547 lines are removed every day, thereby improving quality and relevancy.
Kernel changes per release by type (added, modified, deleted); Source: Linux Foundation
(Click to enlarge)
Top Linux contributors
Despite the growth of contributors, a relatively small number of contributors continue to do a majority of the work, says the LF. Over the past 4.5 years, for example, the top 10 individual developers have contributed almost 12 percent of the number of changes, and the top 30 developers have contributed over 25 percent, says the group.
Once again, the LF has published a scorecard of the top individual contributors to the Linux kernel, measured in number of changes. The top five contributors remain largely the same as in April 2008, although in a slightly different order, with David S. Miller leading the list. Falling off the list from last year are Linux superstar Andrew Morton, who has dropped to number 10, and Ralf Baechle, who has fallen to number seven. The new top five ranking includes real-time expert Ingo Molnar, as well as Takashi Iwai.
The top 5 Linux contributors, and their number of changes since April 2008, are said to be:- David S. Miller -- 2,239
- Ingo Molnar -- 2,125
- Al Viro -- 1,981
- Adrian Bunk -- 1,883
- Takashi Iwai -- 1,801
Linus Torvalds, meanwhile, has fallen off the top 30 list, says the LF. However, the study notes that the original Linux developer is still a major contributor. It also notes that the list does not include "merge commits," when one set of changes is merged into another, where Torvalds is said to play a key role. In addition, the growing acceleration of kernel development has increased the time Torvalds spends reviewing other kernel changes.
Linux 2.6.31 released
Last week Torvalds announced a stable RC6 version of the 2.6.31 kernel. This maintenance release is not nearly as newsworthy as the 2.6.30 kernel released in June or the 2.6.29 kernel announced in March, notes Torvalds. "There's nothing hugely interesting there," he continues, "although I'm personally gratified by the fact that I have a few more commits than usual. Even if they are all really small, it makes me feel useful."
Noting that "things do seem to be calming down," he characterizes the changes as representing "lots of small fixes all over, spread out fairly evenly." Half of the changes are said to be related to drivers, and there are roughly 10 percent each in "arch, fs, kernel, tools/perf, and 'rest', writes Torvalds. Some of the more notable changes are said to include additional i915 displayport patches, a few perf-counter patches, and a null pointer fix.
Availability
The free Linux Foundation report update, "Who Writes Linux?" may be found in a PDF, here. Linus Torvalds' report on the 2.6.31 kernel on Linux.com should be here
Corbet and Kroah-Hartman will participate on a panel at LinuxCon, discussing the new study and exploring the kernel development process. Torvalds and kernel community members James Bottomley, Arjan van de Ven, and Chris Wright will join them on LinuxCon's keynote panel on Sept. 21, at 2PM PT.
-- Eric Brown
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