Understanding the Linux Kernel

16.8. Anticipating Linux 2.4

Swapping must now take into consideration the existence of RAM zones; much of the swapping code has thus been rewritten in a simpler and cleaner way, mainly thanks to the new page cache implementation. The swap cache is still implemented on top of the page cache, but the swapper_inode fictitious inode object has been replaced by a file address space object. The kpiod kernel thread has been removed, because it is now safe to directly swap out pages of shared memory mappings. Moreover, the arrays of locks associated with each swap area are no longer used.

The most interesting change concerns the policy used to select the process from which stealing pages when reclaiming memory: it is the one that performed fewer page faults (recall that in Linux 2.2 it is the one that owns the largest number of page frames).