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See also: last week's Kernel page.

Kernel development

The current development kernel version is 2.3.18, released on September 10. This is a relatively small patch for modern times - just over 1MB uncompressed, changing 401 files. But it has some interesting stuff:
  • After many years, PCMCIA support has been integrated into the mainline kernel. At this point the structure is there, but most of the actual drivers themselves are not. It will take some adjustments to each driver to make it work in the new integrated scheme; David Hinds, master of PCMCIA, has requested that people not jump in and start converting individual drivers until he has figured out a consistent and sustainable way of doing the work.

  • The Direct Rendering Manager (DRM) has also been put into the kernel. DRM is the kernel-level support needed for the Direct Rendering Infrastructure (DRI), which will be part of XFree86 4.0. Essentially, DRI pushes the handling of three-dimensional rendering into the X server. The server, in turn, can take advantage of the rendering capabilities provided by the video hardware. The result should be secure access to low-level hardware and screamingly fast 3D graphics. More information on DRM can be found on the DRM design document; DRI in general is discussed in this document.

All of the above, however, was overshadowed by the other news: the 2.3 feature freeze is now in effect. Linus announced his intention to get the freeze off to a solid start by taking a two-week vacation, and dumping all of his mail when he gets back. So there is no point in even trying to get him to incorporate new features into the system.

The plan is that the freeze turns into a hard code freeze in a couple of months, with a release still set for the end of the year. Maybe we really will have a "stocking stuffer" kernel for Christmas this time around.

Alan Cox has restarted his "ac" kernel patch series in the hope of having a coherent set of fixes to pass to Linus after the vacation. The "ac" series is intended to only include patches which fit within the feature freeze constraints, so there will be no exciting new features found there. The current patch of this writing is 2.3.18ac5.

The current stable kernel release remains 2.2.12. Alan Cox is active in this field as well; he has a 2.2.13 prepatch up to version 8. Alan's stated intent is to try to make a "rock solid" 2.2.13 - something which would certainly be much welcome in the user community. If that works out, then 2.2.14 can get the knfsd patches (discussed last week).

Low latency and multimedia applications. Paul Winkler pointed us this week at Benno Senoner's low-latency mini-howto out there on the web. Latency, in this case, is the period of time that an application has to wait to get access to the CPU when it has something to do. Multi-user operating systems have tended to have relatively long latencies, making it hard to run applications that must respond to events within one millisecond (or less).

Benno has recently posted some results from his latest tests, which incorporate the work of, primarily, Ingo Molnar. His results: sub-millisecond response times are now possible with Linux, and even the longest latency (500 microseconds) looks like something that should be fixable, once somebody can figure out what is going on. The end result is that Linux is well on the path toward becoming a solid multimedia platform, without the need for real-time hacks and other trickery.

Other patches and updates released this week include:

  • A patch to MTRR by Zoltan Boszormenyi to make it work properly on Athlon and Cyrix processors.

  • Devfs v121 from Richard Gooch. Richard also put out Devfs 99.5, which is a backport of the latest devfs to the 2.2 kernel.

Section Editor: Jon Corbet

September 16, 1999

For other kernel news, see:


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