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Linux Kernel Development Speeds Up

More developers are contributing more code to the development of Linux, and are speeding up in the process, according to a new study from the Linux Foundation.

The latest "Who Writes Linux" report is now its second year, tracking the development of Linux from the 2.6.24 kernel to the recent 2.6.30 kernel release.

The report found that that there Linux saw a net increase of 2.7 million lines of code between the 2.6.24 and 2.6.30 releases, compared to the almost 300,000 lines added in the run-up to 2.6.24.

That code was contributed to Linux at a faster rate and by more developers than the previous release, the report also found.

The pace of development, measured in terms of patches accepted every hour, was 42 percent faster than it had been in the first Who Writes Linux report. Between the 2.6.24 and the 2.6.30 releases, there were 5.45 patches accepted every hour, for an average of 10,923 lines of code added every day, the Foundation said.

New code contributions have included additional hardware support as well as operating system features such as next-generation filesystems like BTRFS.

While new code is added, old code is also pruned away. The report found that an average of 5,547 lines of code are removed every day.

Who is doing all the work?

Since the first Who Writes Linux report last year, the average number of individual developers who contribute to Linux has grown more than 10 percent: The 2.6.30 Linux kernel release had 1,150 developers while the 2.6.24 release had 1,057 developers.

Over the course of the last four and a half years, between the 2.6.11 kernel in 2005 and the 2.6.30 kernel release this year, a total of 4,190 individuals contributed.

But those figures don't tell the whole story, according to the Foundation.

"Despite the large number of individual developers, there is still a relatively small number who are doing the majority of the work," the report said. "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 percent of the number of changes and the top 30 developers have contributed over 25 percent."

Surprisingly, Linux founder Linus Torvalds is no longer among the top 30 Linux contributors over the course of the last year, as measured by the total number of changes. Since the 2.6.24 kernel, Torvalds contributed 254 changes. In contrast, Red Hat kernel developer Ingo Molnar contributed 1,164 changes between the 2.6.24 and the 2.6.30 kernel releases.

"Linus remains an active and crucial part of the development process; his contribution cannot be measured just by the number of changes made," the report said.

Torvalds' contribution also can be seen in kernel merges. The report's patch contribution numbers do not count "merge commits," which is where the patch changes are merged into other changes in the Linux kernel. Since the 2.6.24 release, Torvalds directly managed 2.7 percent of all Linux kernel merges, ranking him ninth on the list of top developers that merged or signed-off on code for inclusion in Linux.

Top companies contributing

In terms of the top companies that contributed to the 2.6.30 release, Red Hat (NYSE: RHT) ranked No. 1, with 12 percent of all change contributions. IBM (NYSE: IBM) came in at second place with 6.3 percent, Novell (NASDAQ: NOVL) third at 6.1 percent and Intel (NASDAQ: INTC) fourth at 6.0 percent.

While developers with company affiliations contribute many changes to Linux, the report found that 21.1 percent of all changes since the 2.6.24 kernel came from developers with no corporate affiliation. In the previous study, the Linux Foundation reported only 13.9 percent of developers as having no corporate affiliation. At least part of the increase may come from simply improved data-collection.

"The increase in the number of developers with no employer is most likely an artifact of better information in our database -- many of them were previously in the 'unknown' category," the report said.

The 2008 report stated that developers whose corporate affiliation is unknown represented 12.9 percent of Linux kernel changes. In the new report, the unknowns now only represent 4.2 percent.