Kernel release 2.6.11 of March 2005 had 475 developers, and the upcoming 2.6.22 release this month has 920 developers, Kroah-Hartman said.
The number of kernel changes is also growing. While 2.6.11 had about two changes per hour, 2.6.22 is at four changes per hour. And even when Linus Torvalds took a month off to write the git revision control system in the spring of 2005, the rate of change was faster than the entire 2.5 "development" tree. "We are going up. We are going faster than we have before,” Kroah-Hartman said. “This scares the heck out of traditional computer scientists."
Despite Red Hat's dominance of commercial Linux sales, the spread of actual development contributions is much more diverse, with Novell, where Kroah-Hartman works, punching above its weight at 9.7% of contributions to Red Hat's 11.8%. The next three companies in the rankings are IBM, Intel and SGI, which has installed a 4096-processor supercomputer, the largest single system image Linux box yet.
But just above SGI in the listings are what Kroah-Hartman calls "amateurs". Although the great independent Linux hacker has been thought extinct, known amateurs still count for 3.9% of kernel changes. Reflecting the large number of small changes, the top category is still "unknown", but everyone with 10 or more changes in the kernel is accounted for, Kroah-Hartman said.
The large contributor base, huge code base (8.2m lines) and rapid change means that it is impossible to maintain quality kernel space code for Linux outside the development process. Kroah-Hartman said: "You're never going to be able to catch up. It's just physically impossible. If your company isn't showing up here and you need to affect how Linux is developing in the future, you need to get involved."