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Linux's work to scale vertically?

Slashdot and other sites had mention of the release of the 2.6.27 Linux kernel today. Some of the new features in the kernel come from the KernelNewbies Linux 2.6.27 notes about improved SMP support for the page cache: The page cache is the place where the kernel keeps in RAM a copy of a file to improve performance by avoiding disk I/O when the data that needs to be read is already on RAM. Each "mapping", which is the data structure that keeps track of the correspondence between a file and the page cache, is SMP-safe thanks to its own lock. So when different processes in different CPUs access different files, there's no lock contention, but if they access the same file (shared libraries or shared data files for example), they can hit some contention on that lock…