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Solution to the Fall 2012 Second COSC 6360 Quiz

Solution to the Fall 2012 Second COSC 6360 Quiz. Jehan-François Pâris jparis@uh.edu. ARC. Consider a very small cache that can hold only 4 pages and assume that the cache is managed by the ARC replacement policy. How would target_T 1 be affected if the next page to be referenced is:

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Solution to the Fall 2012 Second COSC 6360 Quiz

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  1. Solution to the Fall 2012 Second COSC 6360 Quiz Jehan-François Pâris jparis@uh.edu

  2. ARC • Consider a very small cache that can hold only 4 pages and assume that the cache is managed by the ARC replacement policy • How wouldtarget_T1 be affected if the next page to be referenced is: • Page 5? • Page 6?

  3. Answer • Consider a very small cache that can hold only 4 pages and assume that the cache is managed by the ARC replacement policy • How wouldtarget_T1 be affected if the next page to be referenced is: • Page 5? No change • Page 6?Decreased

  4. Similar question • Consider a very small cache that can hold only 4 pages and assume that the cache is managed by the ARC replacement policy • How wouldtarget_T1 be affected if the next page to be referenced is: • Page 7? • Page 2?

  5. Answers • Consider a very small cache that can hold only 4 pages and assume that the cache is managed by the ARC replacement policy • How wouldtarget_T1 be affected if the next page to be referenced is: • Page 7? Increased • Page 2?No change

  6. TLB issues • A computer has a TLB with 128 entries and uses 8 KB pages. What is the coverage of its TLB?

  7. Answer • A computer has a TLB with 128 entries and uses 8 KB pages. What is the coverage of its TLB? • Coverage = 1288 KB = 1 MB • If page size was 4KB • Coverage = 1284 KB = 512 KB

  8. Proof-carrying code (I) • Which problem does proof-carrying code (PCC) attempt to solve?

  9. Answer • Which problem does proof-carrying code (PCC) attempt to solve? • To let kernels to check extension safety a extension load time • The idea is to eliminate any kind of run-time checking overhead

  10. Proof carrying code (II) • What is the main drawback of the approach?

  11. Answer • What is the main drawback of the approach? • It is very difficult to construct safety proofs for non-trivial extensions

  12. Mach VM system (I) • How does the Mach virtual memory subsystem guarantee exclusive access to its data structures?

  13. Answer • How does the Mach virtual memory subsystem guarantee exclusive access to its data structures? • It uses locks whenever exclusive access to a data structure has to be guaranteed.

  14. Mach VM system (II) • How does it prevent deadlocks?

  15. Answer • How does it prevent deadlocks? • All VM algorithms gain locks using the same ordering.

  16. More Mach • Give one example of a Mach memory object.

  17. Answer • Give one example of a Mach memory object. • A swap area • Any file of the file system • Could be • Executable file for a running program • A file being mapped

  18. Treadmarks (I) • Treadmarks is said to use a lazy release policy. Why?

  19. Answer • Treadmarks is said to use a lazy release policy. Why? • Delays propagation of release values until an acquire is issued

  20. Treadmarks (II) • What would be the corresponding eager release policy?

  21. What would be the corresponding eager release policy? The policy would immediately propagate all released values to all other processes Answer

  22. Example Eager release Lazy release

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