KS2012: Improving development processes: linux-next

The final session of day one of the 2012 Kernel Summit considered the linux-next tree and a possible complementary tree.

Steven Rostedt stated that he'd like to have a "linux-devel" tree, which would serve a similar purpose to that once served by Andrew Morton's "-mm" tree: it would be a place where reasonably stable code sits for a while for longer testing. He noted that such a tree might be useful for an API that hasn't yet stabilized, for example. Steven asked whether others would also be interested in something like this.

Chris Mason questioned whether such a tree could work in practice. "When your work and my work are together, people blame me for your bugs and vice versa." Based on experience with a similar approach in another project, Ben Herrenschmidt noted another problem: people started developing against that code base instead of the designated development base (i.e., the creation of a "linux-devel" might cause some people to develop against that tree instead of linux-next). Tony Luck noted that the value of a "linux-devel" tree would depend greatly on how much testing it received, and the sense was that such a tree would likely see less testing than linux-next, which itself could do with more testers.

Of course, even if a "linux-devel" tree was considered worthwhile, the tree would need a maintainer. In response to the question of how much work was required to maintain linux-next, the maintainer, Stephen Rothwell, said it required between four and ten hours per day, depending on the stage in the kernel-release cycle. In the end, as Steven Rostedt himself noted, the overall response to the proposal of a "linux-devel" tree was unenthusiastic.

Attention then briefly turned to the linux-next tree. Ted Ts'o asked: are people happy with how the tree was working? The overall consensus seemed to be that it was working well. H. Peter Anvin seemed to sum up the mood, in stating his overall contentment with linux-next while noting that "the imperfections of linux-next are reflections of the fact that it is a real-world creation". Ted asked in a tone that seemed to expect a negative answer, "does anyone run linux-next in anger on their development system?", and was a little surprised to see that quite a number of kernel developers indicated that they do eat their own dog food, living pretty much continuously on linux-next as the booted kernel on the work system that they use on a daily basis. After more than three years, it's clear that linux-next is by now an essential part of the kernel-development model.