[理工] [OS]-page fault
Consider the two dimensional array A
int A[][]=new int [50][50];
Where A[0][0] is at location 100,A[0][1]=102,A[0][3]=104...,in a paged
system with pages of size 100 bytes. A small process is in page0(locations 0
to 99)for manipulating the matrix; thus, every instruction fecth will be
form page 0
Assume that there are five pages frames; page frame 1 has the process in it
and the other four are initially empty. Consider two different page
replacement algrithoms: FCFS and LRU, and the following loop.
for(int j=0;j<50;j++)
for(int i=0;i<50;i++)
A[i][j]=0;
(1)列出這個迴圈的page reference string
(2)對於每一個 replacement algrithms共有幾次page fault?
我的解法是： 陣列在記憶體的排列是row major，而且一列等於1個page
(1) 所以page reference string是 0 1 0 2 0 3...49
0 1 0 2 0 3...49 (不確定)
.
.
(2) 50*50＝2500
第一題要怎麼看？每一次指令fetch 到底是怎樣算一次？ 是for
for
A[][] 一次全部？
還是只有 A[][]？ 指令fetch到底是抓多少，我第一題對嗎..？
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