Examining Linux 2.6 Page-Cache Performance

Examining Linux 2.6 Page-Cache Performance

Given the current trends towards ubiquitous 64-bit server/desktop computing with large amounts of cheap system memory, the performance and structure of the Linux page-cache will undoubtedly become more important in the future, and we believe an analytical and empirical examination of performance will be valuable in guiding future development.

The current 2.6 radix-tree based design represents a huge leap forward from the old global hash-table design, but we also beleive there may be some issues with the current radix-tree structure itself.

We have three main concerns about the current implementation:

1) Radix tree keys are unnecessarily long especially on LP64 systems which can cause radix trees to perform poorly

2) The common case of in-order insertion of pages into the radix tree could most-likely be improved

3) Parallel access to the radix-tree structure

We will cover our analysis of the current implementation and discuss potential improvements for these issues using a combination of analytical models and our measurements of improvement using proof-of-concept implementations of ideas such as: extendible hashing techniques, trading space for time by altering the MAP_SHIFT setup, using smaller radix keys combined with larger logical page sizes, and possibly others.