Stories about: CFS

Chris Mason has recently released Btrfs v0.10, which contains a number of interesting new features. In general, Btrfs has come a long way since LWN first wrote about it last June. Btrfs may, in some years, be the filesystem most of us are using - at least, for those of us who will still be using rotating storage then. So it bears watching.

Jonathan Corbet is an active kernel contributor, co-founder and president of Linux development community news site LWN.net, and the lead author of Linux Device Drivers, Third Edition. His renowned Kernel Report has been presented to audiences worldwide, and this year marks his fourth appearance at Linux.conf.au. Here, Corbet offers Computerworld readers a sneak peek at the major themes behind this year's Kernel Report.

The Completely Fair Scheduler (CFS) was merged for the 2.6.23 kernel. One CFS feature which did not get in, though, was the group scheduling facility. Group scheduling makes the CFS fairness algorithm operate in a hierarchical fashion: processes are divided into groups, and, within each group, processes are scheduled fairly against one another. At the higher level, each group as a whole is given a fair share of the processor. The grouping of processes is done in user space in a highly flexible manner; the control groups (formerly "process containers") mechanism allows a management daemon to classify processes according to almost any policy.

While the kernel 2.6.23 development cycle has not yet run its course, things are getting close enough to the end that it makes sense to start looking at the overall statistics for this release. As of this writing (shortly after 2.6.23-rc6 came out), just over 6,200 non-merge changesets had been added to the mainline kernel repository. These changesets came from 854 developers - a slightly smaller number than we saw for 2.6.22. Just over 350 of those developers contributed one single changeset.

It has been almost two years since LWN covered the swap prefetch patch. This work, done by Con Kolivas, is based on the idea that if a system is idle, and it has pushed user data out to swap, perhaps it should spend a little time speculatively fetching that swapped data back into any free memory that might be sitting around. Then, when some application wants that memory in the future, it will already be available and the time-consuming process of fetching it from disk can be avoided.

Linus Torvalds, creator and maintainer of the Linux operating system kernel, has reacted angrily to suggestions that the kernel's development process is skewed in a way that prevents improvements on the desktop.