cs533 concepts of operating systems class 14
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CS533 Concepts of Operating Systems Class 14. Extensible Virtual Memory Management. Questions. What is an inverted page table? Why are they good for large sparse address spaces? - PowerPoint PPT PresentationTRANSCRIPT
CS533 Concepts of Operating Systems
Class 14
Extensible Virtual Memory Management
CS533 - Concepts of Operating Systems 2
Questions
What is an inverted page table?o Why are they good for large sparse address spaces?
How are address maps, memory allocation queues, memory object lists, memory objects, resident page tables, and pmap used to
o Handle a page fault?o Page out a page?o Allocate memoryo Deallocate memory
CS533 - Concepts of Operating Systems 3
Questions
Why does Mach distinguish between current and maximum protection for pages?
Why are shadow objects needed?o How would task A share a page copy-on-write with task
B?o Why might you end up with long chains of shadow
objects?o Why is this a problem?o How could you optimize them?
CS533 - Concepts of Operating Systems 4
Questions
How can Mach support lazy modification of pmap?
Why don’t inverted page tables support aliasing well?
What three strategies can Mach use to maintain TLB consistency on multiprocessors that do not support inter-CPU TLB flush operations?
o Which one reminds you of RCU and why?
CS533 - Concepts of Operating Systems 5
Questions
Why push virtual memory fault handling to user level?
o What kind of user-level instructions can it replace?o Is it always more efficient to use VM faults than user-
level interpretation?o What are the performance trade-offs?
CS533 - Concepts of Operating Systems 6
Questions
Why are these technique more difficult to use on modern CPUs with deep pipelines, out of order instructions and weak memory consistency?
Why do hardware details such as physically vs virtually indexed caches affect aliasing costs?
Why do OS details such as inverted page tables affect aliasing costs?