Building a software based MMU and TLB

Question

Hello guys,

I am trying to hack an old unix kernel. I just want to implement the MMU and TLB using software. Can some one tell me what are the best Data structures and algorithms to use in building one. I saw lots of people using splay trees because its easy to implement LRU. Is there any better Data Structure ? What is the most efficient way of translating virtual to physical address in software.Assume its x86 architecture and translation as any basic page table translation.

Thanks & Regards,

Mousey.

Answer 1

You mention efficiency. Is that the goal you're engineering towards? If you're not constrained to any particular goal, just try to get it working. I'd do a single level page table if you can, either direct or fully associative. It sounds like you're past this though.

Most efficient is going to depend on size-speed tradeoffs and what kind of locality you expect. Do you have any critical apps profiled or is this just messing around to try out some implementations? Inverted page tables are used on some newer architectures. I would take that as an indication that someone spending a lot of time working on this thinks it's a good way to go.