운영체제1장.5장.9장연습문제

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운영체제1장.5장.9장연습문제에 대한 보고서 자료입니다.

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computer provides its users with a virtual memory space of 2(32exp) bytes. The computer has 2(18exp) bytes of physical memory. The virtual memory is implemented by paging, and the page size is 4,096 bytes. A user process generates the virtual address 11123456. Explain how the system establishes the corresponding physical location. Distinguish between software and hardware operations.
Answer : The virtual address in binary form is
0001 0001 0001 0010 0011 0100 0101 0110
Since the page size is 2(12exp), the page table size is 2(20exp). Therefore the loworder 12 bits "0100 0101 0110" are used as the displacement into the page, while the remaining 20bits "0001 0001 0001 0010 0011" are used as the displacement in the page table.
9.6 Is it possible for a process to have two working sets, one representing data and another representing code? Explain.
Yes, in fact many processors provide two TLBs for this very reason. As an example, the code being accessed by a process may retain the same working set for a long period of time. However, the data the code accesses may change, thus reflecting a change in the working set for data accesses.
9.7 Suppose that your replacement policy (in a paged system) is to examine each page regularly and to discard that page if it had not been used since the last examination. What would you gain and what would you lose by using this policy rather than LRU or second-chance replacement?
Answer Such an algorithm could be implemented with the use of a reference bit. After every examination, the bit is set to zero; set back to one if the page is referenced. The algorithm would them select an arbitrary page for replacement from the set of unused pages since the last examination. The advantage of this algorithm is its simplicity-nothing other than a reference bit need be maintained. The disadvantage of this algorithm is that it ignores locality by using only a short time frame for determining whether to evict a page or not. For example, a page may be part of the working set of a process, but may be evicted because it was not referenced since the last examination (that is, not all pages in the working set may be referenced between examinations.)

키워드

운영체제,   운영체제연습문제,   운영체제1장연습문제,   운영체제9장연습문제,   운영체제5장연습문제