What's new in Linux 2.6.32
by Thorsten Leemhuis
3D support for newer Radeon graphics chips, better use of power saving features offered by the latest hardware and numerous enhancements to KVM and Btrfs are some of the outstanding items among the many thousands of changes undertaken for the latest kernel version. Various other improvements should also make Linux 2.6.32 more reactive and as a result, feel faster.
Nearly three months after the release of Linux kernel 2.6.31, Linus Torvalds has now put the lid on Linux 2.6.32 development. Like its predecessors in the main development tree, the new version includes a plethora of new features. The close collaboration between AMD's graphics chip department and the open source community has borne further fruit, with Linux 2.6.32 now enabling 3D support and kernel-based mode setting (KMS) on the widely-used Radeon 2000, 3000 and 4000 series graphics cards.
Also new in Linux 2.6.32 is KSM, which merges identical memory pages from different userland processes to reduce memory usage in virtualised environments and make more efficient use of hardware. Devtmpfs should mean that the Linux kernel boots faster and no longer requires udev, while new make targets will allow testers to easily generate kernel configurations adapted to their systems.
There is also now support for Intel's Moorestown platform, SFI (its alternative to ACPI), ACPI 4.0 and Trusted Execution Technology (TXT – previously known as 'LaGrande') Some major changes to the power management code lay the foundations for making better use of runtime power saving features on modern I/O devices. Various enhancements to the Cpuidle framework, the block layer and Btrfs also offer hope of higher data throughput rates. Linux 2.6.32 should not only allow PCs to push more data around, it should also feel faster, with changes to the block layer and the process scheduler promising better reactivity.
The Kernel Log which follows gives an overview of these and many other changes in the newly released Linux kernel. Even those Linux users who take little interest in their Linux distribution's kernel will also eventually benefit from these changes, as future distributions will utilise Linux 2.6.32 or its successors.
The kernel and its Direct Rendering Manager (DRM) will now offer 3D support and kernel-based mode setting (KMS) for AMD's series R600 and R700 GPUs. These are used in the Radeon series 2000, 3000 and 4000 models – which includes most of the Radeon graphics cards sold in the past couple of years as well as various AMD series 700 motherboard chip-sets. For the 3D support and KMS to function, however, suitable (developer) versions of Libdrm and Mesa 3D as well as Radeon graphics drivers for X.org need to be installed. Compiling this software stack is a task for advanced users – the recently released Fedora 12 already has everything needed, post install only the experimental Mesa support must be added from the repositories.
The "video=" parameter in the KMS code can now be used for setting a specific output screen resolution for either individual monitors, or for all monitors. The Intel KMS code will now compress the frame buffer, which reportedly reduces power consumption by up to 0.5 watts; in addition, the new "Dynamic Clock Frequency Control" feature is intended to further reduce power consumption by reducing the LCD refresh rate, the memory's self refresh and the clock rate to prolong notebook battery life.
The kernel hackers have also integrated the VGA arbitration patches (1, 2, documentation). In systems with several graphics cards, the patches cooperate with X Servers from version 1.7 to ensure that the respective graphics card will actually receive the VGA commands sent to it by the X Server – which reportedly allows much more flexibility when implementing multi-seat environments.