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What's new in Linux 2.6.34

by Thorsten Leemhuis

Two new file systems, improved support for the power saving techniques offered by modern hardware, and many new or extended drivers are only some of the hundreds of advancements that characterise the new kernel version.

Linus Torvalds has released version 2.6.34 of the Linux kernel. Like version 2.6.33, which was released about three months ago, and the version before that, this latest kernel in the Linux main development branch offers numerous improvements to the kernel infrastructure as well as hundreds of new and improved drivers.

For instance, Linux 2.6.34 supports two new file systems and can address a few very recent or soon to be expected graphics chips that were not supported in older kernel versions. Various new technologies are to increase data throughput in the communication between guest systems and the outside world. Several other improvements enhance the Linux kernel's utilisation of the power saving mechanisms found in modern hardware.

This Kernel Log offers an overview of these and many further new features of Linux 2.6.34. These changes will eventually impact all Linux users because future Linux distributions will be based on Linux 2.6.34 or its successors to ensure the widespread use of new kernels; at the end of this article, the Kernel Log will also take a peek at the advancements some developers have already prepared for Linux 2.6.35.

Graphics drivers

One of the changes with the greatest long-term significance is likely to be the merger of patches which add rudimentary support for the Evergreen/R800 graphics chip to the Radeon DRM driver responsible for kernel-based mode setting (KMS). This will allow the kernel to address many of the Radeon HD-5000 series graphics cards introduced since the autumn which use this graphics chip. The driver doesn't at present make use of the acceleration features offered by these GPUs, but the drivers for older Radeon graphics hardware also started out this way, and they now do a pretty fine job. From 2.6.34, the KMS driver for older Radeon GPUs will be able to activate some of the dynamic power saving features offered by Radeon hardware. Many other enhancements in this area are in preparation for forthcoming versions of the kernel.

The Intel KMS driver in 2.6.34 will already support the graphics cores known only by the codename Sandybridge, which Intel is expected to release early next year. The driver now activates memory self-refresh on Intel 9xx series chipsets when the CPU goes into deep sleep mode. According to the commit comments, this reduces power consumption on an idling netbook containing the 945GSE chipset by 0.8 Watts.

The Nouveau driver for GeForce graphics hardware now includes everything you need to dynamically generate open source firmware for NV50 GPUs on demand, so that 8xxx, 9xxx and GTX2x0 series GeForce graphics chips will now run without the controversial ctxprogs, generated using proprietary graphics drivers. Other major rejigging of the driver including the removal of support for user mode setting (UMS) means that the Nouveau driver for X.org for Linux 2.6.33 will not work with the 2.6.34 kernel and nor will the reverse combination. This kind of incompatible change to driver interfaces with userspace is not normally permitted, but, kernel hackers have decreed, is acceptable in this case because Nouveau is still a staging driver. The Nouveau development team has nonetheless been forced to endure a torrent of criticism from Torvalds on the Linux kernel mailing list. He is particularly concerned that the change makes it harder for testers to switch between different kernel versions in order to find out when a particular bug arose.

On some laptops equipped with both onboard graphics and a separate graphics chip, the kernel can now switch between the two and switch off whichever is not being used in order to save power. 'VGA Switcheroo' currently only works on some laptops and does not offer the ease of use of Windows, as it only switches when X Server is restarted – something which is not expected to change in the near future.

Next: File systems, Networking, PCI and Power

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