FreeBSD/arm Superpages for ARMv7

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Abstract

The objective of this project is to provide FreeBSD/arm with the superpages support.

Indicated functionality is intended to work on all ARMv7 based processors, however the reference hardware platform for this development would be a Pandaboard - a popular system, widely available, based on Cortex-A9 ARMv7 CPU core.

Problem description

ARM architecture is more and more prevailing, not only in the mobile and embedded space. Among the more interesting industry trends emerging in the recent months has been the “ARM server” concept. Some top tier companies started developing systems like this already (Dell, HP).

Key to FreeBSD success in these new areas are sophisticated features, among them are superpages, which allow for efficient use of TLB translations so they cover large physical regions, leading to improved performance in many applications and scalability.

Contemporary ARM architecture (ARMv7, the upcoming ARMv8) is already on on par with the traditional PC architecture in terms of advanced CPU features (MMU, multi level cache, TLB, multi core, hardware coherency and similar) and in particular can make use of transparent superpages support.

M1	Clean-ups of pmap-v6.c module	in progress
M2	Initial implementation of superpages on ARM	started
M3	Performance measurements, testing, documentation	not yet
M4	Final integration with the FreeBSD source repo	not yet