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A number of changes to the write-back code now prompt the kernel to dynamically adjust the amount of written data to the write speed of the storage device so that the system works to capacity without being overloaded (for example 1, 2). Precursors of these patches that worked slightly differently were discussed in the article "Dynamic writeback throttling" on a year ago.

Various modifications to the SLUB slowpaths are designed to improve the performance of SLUB, a function for handing out small memory chunks (for example 1, 2, 3). However, the older SLAB alternative to SLUB still performs better in some areas; further optimisations are in planning to reduce, or even eliminate, this shortfall.

Together with a patch that has been integrated for Linux 3.1, the tool Uname26 can instruct the kernel to present version numbers that begin with "2.6." to other programs. This makes some software co-operate that struggle with the current kernel's two-figure version numbers that begin with 3.


Various restructuring measures now allow the Vsyscall emulation to be influenced via a kernel parameter in order to avoid compatibility problems with analysis tools such as DynamoRIO or Pin. Linux 3.1 will be the first version to support the OpenRISC architecture (for example 1; find further changes in the "minor gems" section). OpenRISC is an open source processor architecture with a set of RISC instructions that was originally developed within but is temporarily being developed in the context of the project.

The Sparc code now supports processors in the UltraSPARC-T3 series (for example 1, 2). By implementing numerous restructuring measures to the ARM code and introducing new work methods, the developers of the Linux kernel's ARM support are trying to fix various problems that were criticised in no uncertain terms by Linus Torvalds a few months ago; this means that developers who wish to introduce new platforms or other major changes may have to meet higher quality requirements. Nevertheless, a variety of advancements has been introduced in the ARM area; among these are support for the Prima2 and Zynq SOCs as well as new Omap and S3C platforms by TI and Samsung.

Power management

The power management code now offers "power domains", which are currently mainly relevant for embedded platforms (for example 1, 2). From Linux 3.1, the tools directory with kernel-related userland software will contain the "cpupower" diagnostic tool. A successor to cpufrequtils, the tool monitors whether the power saving and frequency changing functions of modern processors are being used fully – for instance, whether Intel processors switch to the highest clock speed via TurboBoost when only one or a small number of processor cores are busy.

Next: Minor Gems - Infrastructure

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