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