[理工] OS virtual memory
1.
virtual address = 32 bits
page size = 4Kbytes
a page table entry occupies 4 bytes
問題: How many pages should the OS allocate for the pages tables of a
12 MByte process under the following mechanisms?
(1)one-level paging.
(2)two-level paging.(Assuming that the number of entries in a first-level page
table is the same as that in a second-level page table)
2.
Assume we have a demand-paging memory. The page table is held in
registers. It takes 8 milliseconds to service a page fault if an
empty page is available or the replaced page is not modified, and 20
milliseconds if the replaced page is modified. Memory access time is
100 nanoseconds. Assume that the page to be placed is modified 70 percent
of the time. What is the maximum acceptable page-fault rate for an effective
access time of no more that 200 nanoseconds?
請問我下面這樣列式為什麼是錯的0.0?
假設page fault rate = p
200ns >= (1-p)*100ns+0.7p*(20ms+200ns)+0.3p*(8ms+200ns)
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