Feature set of Linux 3.9 has been established
Experimental RAID 5 and 6 support in the still experimental Btrfs will be one of the major new features of Linux 3.9, expected to arrive in late April. This has become apparent because Linus Torvalds has now issued the first release candidate of Linux 3.9 which, as usual, closes the Linux development cycle's "merge window", the phase during which the developers integrate the majority of changes for the next version. This time, the merge window, which started with the release of Linux 3.8, only lasted thirteen instead of the usual fourteen days.
Linux 3.9 will also include a cache target in the Device Mapper that will allow SSDs to be used as hard disk cache in order to offer accelerated access to frequently used data or temporarily store write operations to the faster SSD. The kernel developers have also updated and extended the code that handles LZO compression; they say that this will significantly increase its speed. In Linux 3.9, the kernel's KVM hypervisor will, for the first time, support the virtualisation features that are available in Cortex A15 processors, which means that this will be the first version to work on ARM CPUs. The next kernel will also run on two further CPU architectures: ARC processors from Synopsys and Imagination's Meta ATP (Meta 1) and HTP (Meta 2) processor cores.
Linux 3.9 will also offer a driver for the series 7000 Wi-Fi components that Intel apparently plans to introduce in a few months – probably in early June, together with notebook processors that include a Haswell core. In the release email for the first release candidate of Linux 3.9, Torvalds mentions that the latest merge window had already had more risky moments than usual – including one which affected Ext4 filesystems that are larger than 512GB. However, Torvalds said that the bugs were soon corrected and thanked the testers and kernel developers for being so responsive.
The developers not only provided the first release candidate of Linux 3.9 at the beginning of the week, they have also made available new Stable and Longterm kernels (Linux 3.0.68, 3.4.35 and 3.8.2). The new versions contain the usual bug fixes and minor improvements that carry a very small risk of introducing new problems. Like their direct predecessors, which were released a few days earlier, the new kernel versions 3.4.35 and 3.8.2 plug a security hole that enabled users to escalate their privileges to root level. The same is also true for Linux 3.7.10, released in late February, although the developers have discontinued the maintenance of kernel series 3.7 with this version.
The project's web site kernel.org was also given a new look that is significantly more modern than the old design that had graced the site for years. The web interface for the Git repositories – such as that for the Linux main development branch – are now provided through Cgit. The updated web site also offers more information than before: for example, it includes an FAQ, as well as a page that provides an overview of all currently maintained kernel series.