Feature set of Linux 3.10 defined

Version 3.10 of the Linux kernel will include the bcache block layer cache that allows SSD cards to be used for caching significantly slower but higher capacity hard disks. Developed by a Google employee and used at Google, bcache is the second such feature to be integrated into the Linux kernel; the first one was dm-cache, which the Linux kernel has offered since version 3.9 was released two weeks ago.

The Radeon drivers for Linux 3.10 will include interfaces to address the Unified Video Decoder (UVD) that has been part of Radeon HD graphics cards since the HD 4000 generation; suitable userspace drivers for the video accelerator are planned for the next major Mesa 3D release, which will be given version number 9.2 or 10.0.

"Full dynamic ticks" allow certain Linux 3.10 configurations to reduce the timer interrupt's trigger frequency from between a hundred and a thousand (depending on kernel configuration) to one interrupt per second – this will reduce the kernel's interrupt processing load. In its current form, this feature is mainly relevant for real-time systems and in High Performance Computing (HPC); further changes that are being planned will allow desktop systems to benefit from the feature in the medium term.

Linux 3.10 is expected to arrive in late June/early July, as Linus Torvalds made the first release candidate of Linux 3.10 available last weekend. This release, as usual, marked the end of the merge window phase of the development cycle during which most of the major changes for each new version are integrated into the main code base. With 11,963 commits, Torvalds and his co-developers have integrated more changes than have ever been processed in a merge window before, prompting Torvalds to declare: "this is the biggest -rc1 in the last several years (perhaps ever)". However, diffstat's number of new and removed lines of code is only slightly higher than in Linux 3.9 and is far from being a new record.

In addition to Linux 3.10-rc1, the developers also released long-term kernel versions 3.0.78 and 3.4.45, as well as stable kernel versions 3.8.13 and 3.9.2, last weekend. These releases offer the usual bug fixes and minor, harmless improvements.

The maintenance of Linux 3.8 will be discontinued with version 3.8.13; in the release announcement, Greg Kroah-Hartman writes that users should now migrate to kernel version 3.9. In his email, he again points out that kernel version 3.8 will not be a long-term kernel. Which particular version will be given this status will likely only emerge in the second half of 2013: if all goes according to plan, Kroah-Hartman will discontinue the maintenance of Linux 3.0 in October and award long-term status to a stable kernel that is current at that time; he will then maintain this kernel for two years.

(fab)