1 最差适应算法
2 #ifdef USING_WORST_FIT
3 {
4 //先找到第一个满足要求的空洞，
5 //再以第一个为标准寻找最适合的空洞。
6 //当最适合的空洞完全吻合
7 //就直接划给它，当空洞较大时就切割。
8
9 //首先注册目标指针、目标前一个指针、头指针
10 //记录目标大小和目前最适合大小
11 register struct hole *hp;
12 register struct hole *prevAim_ptr;
13 register struct hole *Aim_ptr;
14 phys_clicks old_base;
15
16 //如果循环一次都没找到
17 //就把可以退出内存的进程赶出去
18 //再循环 ;
19 do{
20 hp = hole_head;
21 prevAim_ptr = NIL_HOLE;
22 Aim_ptr = NIL_HOLE;
23
24 for(;hp != NIL_HOLE && hp->h_base < swap_base;
25 prevAim_ptr=hp,hp=hp->h_next)
26 {
27
28 //当从没记录过合适内存时
29 //把遇到的第一个合适节点保存在aim中
30 if(hp->h_len >= clicks && Aim_ptr == NIL_HOLE)
31 {
32 Aim_ptr=hp;
33 }
34
35
36 //当找到一个比原来aim更合适的空间
37 //记录新的空间
38 if(hp->h_len >= clicks && hp->h_len > Aim_ptr->h_len)
39 {
40 //mark it down
41 Aim_ptr=hp;
42 }
43
44 }
45
46 //we found bigest
47 if(Aim_ptr!=NIL_HOLE)
48 {
49 old_base =Aim_ptr->h_base;
50 Aim_ptr->h_base+=clicks;
51 Aim_ptr->h_len-=clicks;
52
53 /* Remember new high watermark of used memory. */
54 if(Aim_ptr->h_base > high_watermark)
55 high_watermark = Aim_ptr->h_base;
56
57 return(old_base);
58 }
59
60 }while(swap_out());
61 return(NO_MEM);
62 }
63 #endif
1 最佳适应：
2 #ifdef USING_BEST_FIT
3 {
4 //先找到第一个满足要求的空洞，
5 //再以第一个为标准寻找最适合的空洞。
6 //当最适合的空洞完全吻合
7 //就直接划给它，当空洞较大时就切割。
8
9 //首先注册目标指针、目标前一个指针、头指针
10 //记录目标大小和目前最适合大小
11 register struct hole *hp;
12 register struct hole *prevAim_ptr;
13 register struct hole *Aim_ptr;
14 phys_clicks old_base;
15
16 //如果循环一次都没找到
17 //就把可以退出内存的进程赶出去
18 //再循环
19 do{
20 hp = hole_head;
21 prevAim_ptr = NIL_HOLE;
22 Aim_ptr = NIL_HOLE;
23
24 for(;hp != NIL_HOLE && hp->h_base < swap_base;
25 prevAim_ptr=hp,hp=hp->h_next)
26 {
27
28 //当从没记录过合适内存时
29 //把遇到的第一个合适节点保存在aim中
30 if(hp->h_len > clicks && Aim_ptr == NIL_HOLE)
31 {
32 Aim_ptr=hp;
33 }
34
35
36 //当找到一个比原来aim更合适的空间
37 //记录新的空间
38 if(hp->h_len > clicks && hp->h_len < Aim_ptr->h_len)
39 {
40 //mark it down
41 Aim_ptr=hp;
42 }
43 }
44 //we found it
45 if(Aim_ptr != NIL_HOLE)
46 {
47 old_base = Aim_ptr->h_base; /* remember where it started */
48 Aim_ptr->h_base += clicks; /* bite off */
49 Aim_ptr->h_len -= clicks; /* ditto */
50
51 /* Remember new high watermark of used memory. */
52 if(Aim_ptr->h_base > high_watermark)
53 high_watermark = Aim_ptr->h_base;
54
55 return(old_base);
56 }
57
58 }while(swap_out());
59 return(NO_MEM);
60 }
61 #endif
1 下一个最适合 ：
2 #ifdef USING_NEXT_FIT //161 error
3 {
4 register struct hole *hp, *prev_ptr;
5 static register struct hole *start_ptr;
6
7 phys_clicks old_base;
8 start_ptr = hole_head;
9 Prev_ptr=NIL_HOLE;
10 hp=start_ptr;
11
12 do{
13
14 if(hp->h_next==start_ptr)
15 {
16 return(NO_MEM);
17 }
18
19 while (hp->h_next != start_ptr && hp->h_base < swap_base){
20
21 if (hp->h_len >= clicks) {
22 /* We found a hole that is big enough. Use it. */
23 old_base = hp->h_base; /* remember where it started */
24 hp->h_base += clicks; /* bite a piece off */
25 hp->h_len -= clicks; /* ditto */
26
27
28 /* Delete the hole if used up completely. */
29 if (hp->h_len == 0) del_slot(prev_ptr, hp);
30
31 If((start_ptr=hp->h_next)==NIL_HOLE)
32 Start_ptr=hole_head;
33
34 /* Return the start address of the acquired block. */
35 return(old_base);
36 }
37
38 prev_ptr = hp;
39 hp = hp->h_next;
40
41 If(hp==NIL_HOLE)
42 hp=hole_head;
43 }
44
45 }while(swap_out());
46 }
47 #endif
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Code
FIRST_FIT
*===========================================================================*
* alloc_mem分配内存 *
*===========================================================================*/
PUBLIC phys_clicks alloc_mem(clicks)
phys_clicks clicks; /* amount of memory requested */
{
/* Allocate a block of memory from the free list using first fit. The block
* consists of a sequence of contiguous bytes, whose length in clicks is
* given by ‘clicks‘. A pointer to the block is returned. The block is
* always on a click boundary. This procedure is called when memory is
* needed for FORK or EXEC. Swap other processes out if needed.
*/
register struct hole *hp, *prev_ptr;
phys_clicks old_base;do {
prev_ptr = NIL_HOLE;
hp = hole_head;
while (hp != NIL_HOLE && hp->h_base < swap_base) {
if (hp->h_len >= clicks) {
/* We found a hole that is big enough. Use it. */
old_base = hp->h_base; /* remember where it started */
hp->h_base += clicks; /* bite a piece off */
hp->h_len -= clicks; /* ditto *//* Remember new high watermark of used memory. */
if(hp->h_base > high_watermark)
high_watermark = hp->h_base;/* Delete the hole if used up completely. */
if (hp->h_len == 0) del_slot(prev_ptr, hp);/* Return the start address of the acquired block. */
return(old_base);
}prev_ptr = hp;
hp = hp->h_next;
}
} while (swap_out()); /* try to swap some other process out */
return(NO_MEM);
}
时间： 2024-10-13 02:36:08