What are the various kernel trees for ?

-ac

• Maintainer: Alan Cox Ultra-stable tree for 2.6 series with fixes (security, functionality) for the last stable version. Some of the fixes have already been merged in Linus's tree (the 'official' development tree - at kernel.org), while some others are pending.

-mm

• Maintainer: Andrew Morton Fancy new features and fixes with a focus on VM hacks.

-aa

• Maintainer: Andrea Arcangeli VM updates, a multitude of fixes and various improvements from Andrea.

-dj

• Maintainer: Dave Jones Forward ports of 2.4 bugfixes to 2.5 series, plus some other bits. (a slightly less bloody bleeding edge)

-ck

• Maintainer: Con Kolivas A stable 2.6 based patchset with a focus on performance tweaks to the scheduler and vm, with specific tuning for the desktop to improve system responsiveness.

-osdl

• For data center or carrier grade linux, tuning especially for large machines and high database performance.

-rmap

• Maintainer: Rik van Riel Rmap has a reverse mapping from page frames to virtual mappings mostly in order to make a more predictable VM, to get rid of some worst case VM behaviours and smooth things out. The reverse mappings provide infrastructure to make a more flexible VM possible ... which means that VM strategies in -rmap often change.

-rt

• Maintainer: Ingo Molnar Realtime-preempt is a set of patches for the latest version of the Linux kernel. They bring the pre-emption capability to the next level. It's goal is to make the full fledged Linux kernel have as close to real-time response as possible. (As a warning, though, the realtime preempt patches are under going heavy development and have been for some times. It's not unusual for Ingo to update the realtime-preempt patch several times a day, or even within hours of each other. )

You can also browse the git trees available in http://www.kernel.org/git/