A more recent factor keeping Linux development free of corporate agendas is the very breadth of applicability of Linux that I mentioned earlier. After all, it's challenging enough to write an operating system that's scalable from handhelds to mainframes. Doing so while advancing some hidden non-technical agenda is multiply so. Kernel developers have therefore developed a habit of focusing on what's important to the OS, and have scant patience for non-technical issues.
The corporations who hope to benefit from porting Linux to their hardware therefore have come to realise that their contributions to Linux will be incorporated into the standard kernel based solely on their technical merit. They also know no one else will succeed at slipping something in that undercuts their efforts. In short, they can be sure that only technical hurdles stand in the way of a successful port of Linux to their hardware.
The result of this "virtuous cycle" is an operating system that, with version 2.4, boasts an impressive new set of features for everything from low end to high end platforms.
High end system features
- The Logical Volume Manager has been added. This allows for flexible configuration of disks and other media; allowing, for example, spreading a volume over multiple disks. This is important for handling large database applications.
- Similarly, raw device I/O, without caching, is now supported. Some database management systems prefer to perform their own caching rather than leaving it to the operating system, since they can make use of knowledge of application behavior that an OS alone does not have.
- The number of supported simultaneous processes, which had previously been limited to 4090, is now limited only by the amount of RAM in the system. This factor is important for web servers and other transaction processing systems.
- Large memory (up to 64 GB) and terabyte-sized files are now supported.
- Also, improved multiprocessor support allows Linux to get better performance from high end processing hardware.
On the other hand, not yet integrated into the current standard Linux kernel are journaling file systems, which provide fault tolerance when a failure occurs and the system cannot be powered down properly. One, ReiserFS, seems likely to be included soon and is already provided as part of SuSE's Linux distribution.
Low end capabilities
At the low end of the spectrum, some important capabilities have been added that benefit embedded systems and dedicated intelligent devices . . .- Support for Memory Technology Devices, allows ROM and Flash memory based devices to be accessed in the same way as disks. This is necessary for appliance-like operation of devices and diskless embedded systems, and for high reliability in critical systems.
- Similarly, cramfs provides a compressed read-only file system, and ramfs is a RAM-based file system -- both ideal for ROM or Flash memory based applications.
- More network support had also been added, including support for ARCnet, a venerable (and reliable) network popular in industrial environments.
- Also, support is now included for Intelligent Input/Output (I2O) devices, which is becoming increasingly important for higher-end embedded systems.
Major restructuring
From a developer's perspective, one of the most significant improvements with Linux 2.4 is an intangible: a major overall restructuring of the Linux source code which makes it more modular, configurable, and easier to modify. In fact, reading the Linux 2.4 source code is now a pleasure -- well, at least it is for programmers!Whereas Linux 2.2 was quite difficult (downright painful, really!) to follow, everything in Linux 2.4 is now structured in logical ways. The result is that a reasonably capable programmer can now read, understand, and customize the kernel -- something only the most dedicated specialists could do before.
- Support for Memory Technology Devices, allows ROM and Flash memory based devices to be accessed in the same way as disks. This is necessary for appliance-like operation of devices and diskless embedded systems, and for high reliability in critical systems.
