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- Hyper-Threading, or Fake CPUs
The Pentium 4 and Xeon CPUs do hyper-threading. Hyper-threading emulates multiple CPUs. The 2.6 kernel fully supports it, and unlike Windows 2000, it knows the difference between fake and real processors. So Windows 2000 wants additional CPU licenses for non-existent processors. I think charging per-CPU licenses is absurd in any case. (And so is charging client-access licenses, and depriving customers of “ownership,” while dodging responsibility or liability of any kind…) At any rate, 2.6 takes full advantage of the P4 architecture’s hyperthreading capabilities.
- Bigger and Bigger
PIDs (process IDs) have been boosted from 32,000 to 1 billion. Filesystems, even on 32-bit processors, have a theoretical upper limit of 16 terabytes, up from 4 terabytes. Another nice boost for 32-bit systems is support for 64 GB of RAM, up from 4 gigabytes. Device support has increased tremendously (the /dev directory). In the 2.4 kernel, devices were limited to 255 major numbers, and 255 minor numbers — in effect, roughly 65,000 total devices. The new kernel supports 4,095 major numbers, and more than one million subdevices.
Sound and video are traditional Points of Pain in Linux. Traditionally, on all platforms not just Linux, sound and video drivers introduce instability and other bad behaviors. 2.6 has fully integrated and improved the ALSA (Advanced Linux Sound Architecture). It works harmoniously with multiple processors, and promises to be “thread safe,” which means it won’t trample all over other processes. It supports USB audio, and all kind of audio-nerd things, like full-duplex playback and recording, and multiple sound cards on a single system.
For video-nerds, 2.6 incorporates DVB (Digital Video Broadcasting) support, which means you can build your own Tivo or ReplayTV-type device. Imagine- owning one of these without spyware!
- Other Goodies
- User-Mode Linux, for running multiple Linux virtual machines. User-Mode Linux is great for testing buggy kernels and apps safely, testing all manner of network configurations on a single box, virtual hosting- it’s a Linux lab in a box.
- Support for mounting Novell shares
- ACLs (access control lists)
- Power management is reported to be much better. It had nowhere to go but up.
Linux Kernel 2.6 boasts a lot more great new features, which are listed in the “OSDL 2.6 Press Release” (see below).
Do I Upgrade?
Short answer: Don’t be silly. Like all major kernel releases, 2.6 is mostly backward-compatible, but there are some applications that will not work with the new kernel, without tweaking and patching. The wise admin tests it thoroughly first. One way is to install it on any machine that has the applications you’ll be running on it, right alongside the existing kernel, then select the one you want at boot.
Kernel comparison: Web serving on 2.4 and 2.6
Timeline of the Linux kernel
OSDL Testing Reports
OSDL 2.6 Press Release, lots of good information
Introduction to User-Mode Linux
This article was originally published on CrossNodes.