In Linus Torvalds' words, "Not a whole lot of changes since -rc7," but the more significant upgrades in kernel release 2.6.22, announced over the weekend, include a new wireless stack, a new FireWire stack, and a new SLAB allocator for more efficient memory management.
"For too many years, Linux wireless support has worked, but not very well," according to the folks at Linux Kernel Newbies. "2.6.22 has a completely new, better wireless stack included."
Donated Devicescape, a company that specializes in Wi-Fi software and services, the stack includes full software MAC implementation, Wired Equivalent Privacy/Wi-Fi Protected Access, Quality of Service (QoS) support, hostapd, and 802.11g support.
Drivers are still an issue, however. LK Newbies points out that "the drivers that have been in the tree for a long time do not support this stack, and will need to be ported (which will hopefully not be that hard, since the new stack is actually a much better ground to build drivers upon that the current mess)."
Although the older FireWire stack will be around for awhile, the new one included in this kernel release is said to be leaner and more efficient. It should provide reasonable backward compatibility as well.
The new, slab allocator (SLUB) was written by Christoph Lameter from SGI to address certain efficiency problems. This new allocator, which is not enabled by default, provides better debug capabilities and may enhance performance. Documentation is available.
The folks on the Draconis Software Weblog pointed out the significance of a couple additional new features in this kernel release -- the process footprint measurement facility, which provides "a new way to measure approximately how much memory a process is using," and utimensat(), which provides "the ability to measure file timestamps using nanoseconds for greater precision."
Kernel 2.6.21, released in late April, incorporated the Virtual Machine Interface (VMI), improved the Kernel-based Virtual Machine (KVM), and offered a selection of new device drivers.