The Linux Foundation has released the 2011 edition of its kernel development study. The report provides insight into the status of Linux kernel programming and the level of developer participation. It shows the volume of total growth, the relative number of contributions from major sponsors, and other relevant metrics.

The kernel has continued to see strong growth and developer engagement. The Linux Foundation celebrated the kernel's 20th birthday last year, alongside the release of Linux 3.0. The total size of the kernel grew from 13 million lines of code and 33,000 files in 2010 to 15 million lines of code and 37,000 files in 2011.

The number of developers who are actively contributing to a given version of the kernel has steadily grown from around 400 in 2005 to over 1300 by the end of 2011. Approximately 75 percent of individual contributors are professional software developers who are paid to work on the kernel. Volunteer developers who are known to be contributing without compensation still represent a larger segment of contributions than developers from any given company.

According to the Linux Foundation's statistics, volunteer developers contributed 16 percent of total changes in 2011. Red Hat, which is the most prolific corporate contributor, accounted for approximately 10 percent of changes made to the kernel in 2011. The second largest corporate contributor was Intel, which is responsible for 7.2 percent. IBM and Novell round out third and fourth place.

Despite abandoning the Linux-based MeeGo platform in favor of Windows Phone 7, Nokia still contributed more changes to the kernel than Android and Chrome OS vendor Google. Nokia is reportedly building a new mobile Linux platform of its own called Meltemi, that will be shipped on entry-level smartphones.

A new addition to the list of top contributors this year was Microsoft. The Redmond giant was the 17th most prolific corporate contributor to the Linux kernel in 2011. The company first began contributing code to Linux in 2009 when it submitted patches to improve the performance of running virtualized Linux guest instances on Windows servers.

It was a welcome gesture, but Microsoft wasn't a particularly diligent steward of its contributed code at first. The company had some difficulty meeting the expectations of the kernel developers and doing the work to properly integrate and maintain the code it submitted to the kernel. As kernel developer Greg Kroah-Hartman recently told us in an interview, the issue was eventually remedied.

Microsoft's initial problems working in the upstream kernel community are similar to the issues that Google has run into with its Android kernel contributions. Those were only recently allowed back in the staging area of the source tree after being kicked out a few years ago due to lack of maintenance. In the case of Google's code, it appears that the current effort to get it merged into the mainline is being pursued by third parties.

A graph included in the Linux Foundation report shows how contributions from various companies have evolved over time. Red Hat's percentage of the total changes is decreasing while the volunteer community's is increasing. The graph also indicates the recent rise Samsung and Texas instruments as major contributors, which reflects the growing relevance of the Linux kernel in the consumer electronics industry.

The kernel developers have grown increasingly frustrated with fragmentation in the mobile and embedded hardware ecosystems. The issues with ARM support in the kernel have raised a lot of concerns and eventually became a major topic of discussion in 2011. Organizations like Linaro have emerged to help simplify matters and major component manufacturers are starting to take a more active role upstream.

From supercomputers to smartphones, the Linux kernel is a versatile and widely-used piece of technology. The base of contributors seems to reflects the diversity of Linux adopters. The strength and vendor-neutrality of kernel development illustrates the strength of open governance and participatory development. Readers who want to see the full report can download the PDF from the Linux Foundation's website.