When the system finds it convenient to do so, the system writes the committed changes to the file
system itself. When all the changes have been transferred to the file system, the system can delete
the record of the transaction in the write-ahead log.
If the system should fail some time during this process, the system can look in the write-ahead log
when the system recovers to see what transactions were committed but not yet written to the file
system itself. The system can roll back partially complete transactions.
6.11 If a memory access requires 100 nanoseconds, and the computer uses a page table and virtual memory,
how long does it take to read a word of program memory?
It takes 100ns to read the page table entry, plus 100ns to read the memory location itself. The total
access time is 200ns.
6.12 If we add a TLB to the computer in the previous question, and 80% of the time the page table entry is in
the TLB (i.e., the required memory access results in a ???hit??? in the TLB 80% of the time), on average,
how long does it take to read a word of program memory?
Assuming that TLB access time is negligible:
.8 * ( 100ns ) + .2 * ( 200ns ) = 120ns
6.13 A paging system uses pages with 1024 addresses per page.
Pages:
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527