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11 January 2011, 14:58

Kernel Log: Wonder patch merged, improved AMD and Intel graphic support

by Thorsten Leemhuis

For Linux 2.6.38, the kernel developers have integrated the much-discussed patch which considerably improves the response time of Linux desktops in certain situations. The AMD developers have extended their open source graphics drivers to support various Radeon HD 6000 graphics chips. A discussion was sparked by the tricky situation surrounding the graphics drivers for Intel's new processors.

After the release of Linux 2.6.37 on Wednesday morning, the first patches for kernel version 2.6.38 appeared in the Linux main development branch late on Thursday night. Among Torvalds' first 2,769 commits were the almost 600 patches for the network subsystem that had been submitted by its maintainer, David Miller. As expected, these patches have added the rtl8192ce driver for Realtek's RTL8192CE and RTL8188CE 802.11n Wi-Fi chips to the kernel.

The first changes made for Linux 2.6.38 also include the patch that considerably improves the interactivity of desktop applications in situations where the CPU is fully utilised. This patch became known through such articles as "The ~200 Line Linux Kernel Patch That Does Wonders" on the Phoronix web site; details of the patch's functionality as well as a description of an alternative, more flexible, approach can be found in a previous Kernel Log. The maintainer of the process scheduler, Ingo Molnar, explicitly pointed out this function in his Git-Pull request, calling it "one of the biggest and most visible interactivity improvements achieved by the Linux scheduler".

However, the function is activated via the CONFIG_SCHED_AUTOGROUP option and is disabled in the default kernel configuration settings. Those who add it when compiling their kernel can subsequently turn auto grouping on or off via such commands as "echo [01] > /proc/sys/kernel/sched_autogroup_enabled", or disable it via the "noautogroup" kernel boot parameter when booting. Various other usage tips can be found in the related comment.

Improved Radeon drivers

It appears that a quarter to a third of all major changes for Linux 2.6.38 have already been added to the source code management system, even though the merge window of 2.6.38 has only just begun and will remain open for about 12 more days. Further changes during this time are likely to affect the graphics drivers and provide graphics support for AMD's recently introduced Ontario and Zacate Fusion processors with Bobcat cores, as the related patches can already be found in linux-next.

AMD developer Alex Deucher has released patches which extend the kernel's Radeon DRM driver to support some of the "Northern Islands" (NI) graphics chips found in the series 6000 to 6800 Radeon HD models that have been available since last October. These have now been merged into Linux 2.6.38, so that this kernel version, whose release is expected in late March or early April, will offer 2D and 3D support for these graphics cards. The required userspace code is already available in the developer versions of Mesa3D and in's xf86-video-ati driver package.

Kernel-based Mode Setting (KMS) is required for the new chips, and UMS (User Mode Setting) through the X Server and its driver will no longer be possible with Northern Island chips. The Radeon HD 6000 chips supported by the still emerging code are in various respects similar to the previous generation (Radeon HD 5000 series, code-named Evergreen). The Cayman chips found on the Radeon HD models 6950 and 6970 introduced in mid-December have fewer similarities; according to Deucher, their support is in progress but not yet ready for submission.

Next: Driver problem with new Intel chips

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