Linux kernel org

Ever lose sleep over your system kernel? Not likely—unless, of course, you are a Linux system administrator. Kernels, though not glamorous, provide the underpinnings for any operating system's robustness and performance. The newly released Linux Kernel 2.4, from www.linux.org, promises a new level of scalability on the Linux platform, as well as better compatibility with today's high-speed peripherals.

The reliability of Linux is already legendary, and that reputation is arguably based on the strength of its small, efficient kernel. It has traditionally been limited, however, by its failure to scale onto symmetric multiprocessor (SMP) systems. Although multithreading was added in January, 1999 to the Linux kernel in 2.2, it's been an open secret that this older kernel didn't scale very well beyond two CPUs on a single system. “The scalability fell off after two processors,” says Darren Davis, VP of technology strategy at Caldera. The new kernel promises performance for four CPUs and beyond.

For overcoming obstacles to scalability, the makers of Linux (including its inventor, Linus Torvalds) rewrote the kernel code that worked with such system resources as spin locks, which coordinate access to system resources across multiple CPUs. If implemented inefficiently, spin locks can slow down a multiprocessor system. Kernel subsystems like the networking stack and file I/O are now fully multithreaded.

While previous versions of the kernel were limited to handling 4GB of RAM, the new kernel supports Intel’s 36-bit memory addressing scheme to reach 64GB of RAM.

Other enterprise-level improvements include a fully journaled file system (available in 2.4.1 of this release with the Riser file system), which eliminates the need for time-consuming file system consistency verification on reboots. (This feature contributes to increased server availability.)

The result is a new kernel that’s clearly geared for the enterprise. Both server and desktop versions of Caldera with 2.4 support should be nearing release by the time you read this. Red Hat Linux has had a beta with a 2.4 kernel for several months and has added numerous enhancements to the kernel code base—including its Torvolds Unix standard—which keeps Web server calls in the kernel for better performance. SuSE, another Linux distribution, has already migrated to 2.4. In all, support for 2.4 will be forthcoming soon on virtually all the major Linux distributions.

Unless you are a guru, you probably won’t want to take on building this new kernel yourself. The source files are freely downloadable from www.linux .org, along with many libraries, tools, and tips (including which compiler to use). But you’ll hit more configuration problems than with the more established 2.2 kernel, which has had its build problems shaken out through two years of testing. Most users will want to wait for the official version of the new kernel to arrive with their favorite Linux distribution.

For the desktop, what does the new kernel offer the user? The new kernel has a number of new options for connecting to peripherals. With USB and IEEE 1394 support, Linux will have more reach into cameras, scanners, and even MP3 players. (The source code also describes connecting the new Linux kernel to new Bluetooth devices.)

Getting USB support is only half the battle, however. Vendors have to include software support for Linux. Connecting to your camera is one thing, but getting proprietary devices to communicate is another, taking cooperation between manufacturers and the Linux community. The software to download songs to your favorite MP3 player probably doesn't work with Linux yet. The open source software movement may fill the gap by reverse engineering the protocols used with such devices. Several initiatives are in the works to make this happen (see www.sourceforge.net for details), but don't expect the same level of support for Linux as for more widely used desktop operating systems.

Another less publicized advantage of the new kernel is its support for iptables, which allow for connection-based firewalls. This feature will allow personal firewalls for broadband users.

For administrators planning Web infrastructures, the new Linux kernel support for multiple CPUs may change the way Linux is scaled, because it is now possible to run on fewer (but more powerful) boxes with multiple processors rather than on multiple, cheaper nodes with single CPUs. With this new capability, Linux steps up alongside Sun Solaris and Microsoft Windows. Not that Linux is giving up its “simpler is better” philosophy. Although the new kernel is faster on four-way or eight-way processors, this won't interfere with old-fashioned single-CPU cluster nodes.

We found the 2.4 kernel to be a major upgrade at many levels. The server-side improvements will make this a no-brainer upgrade for anyone running server-side Linux, especially users scaling with multiple CPUs on the same box. For desktop users, don't expect the new kernel to transform Linux into a consumer-oriented OS in the near future. With new connectivity options, however, it is a promising first step toward getting Linux to work with the next generation of digital devices, and this might mean an even friendlier version of the operating system in the future.

Copyright © 2004 Ziff Davis Media Inc. All Rights Reserved. Originally appearing in PC Magazine.