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  • 使用Java模拟操作系统高优先级算法

    最近做操作系统的课程设计，网上看到一些动态调度的算法都是基于C写的，下午闲来无事，用Java写了一个高优先级调度的算法玩玩，这个算法首先有这几条要注意
    • 优先级是否可以为负的，答案是肯定的，如果有一个线程阻塞了另外一个线程一直去运行就可能一直减去，让优先级变成负数了
    • 阻塞的时机：可以说阻塞的时机特别的重要，一旦到达时间需要线程进行阻塞的状态就要立刻将状态改变掉，让它产生调度
    • 恢复成就绪状态的问题：因为是有可能是线程进行I/O操作，让其阻塞了，所以说，一个时间片就需要让恢复阻塞的时间常数+1，当变为0的时候让他进入调度状态
    • 如果在系统中都是阻塞的线程怎么办？那没有办法，操作系统只能干等着让他们变为就绪状态的时候才能运行
    先上一个PCB结构体函数块
    1. public class PCB {
    2. 	//进程的ID
    3. 	private long id;
    4. 	//优先级顺序
    5. 	private int priority;
    6. //	运行的cpu时间
    7. 	private long cputime;
    8. //  需要运行的时间
    9. 	private long alltime;
    10. //  即将阻塞的时间
    11. 	private long startblock;
    12. //	从阻塞中回复的时间
    13. 	private long blocktime;
    15. //	现在线程的状态
    16. 	private String state;
    17. 	
    18. 	
    19. 	public PCB(long id, int priority, long cputime, long alltime,
    20. 			long startblock, long blocktime, String state) {
    21. 		super();
    22. 		this.id = id;
    23. 		this.priority = priority;
    24. 		this.cputime = cputime;
    25. 		this.alltime = alltime;
    26. 		this.startblock = startblock;
    27. 		this.blocktime = blocktime;
    28. 		this.state = state;
    29. 	}
    31. 	public String getState() {
    32. 		return state;
    33. 	}
    35. 	public void setState(String state) {
    36. 		this.state = state;
    37. 	}
    39. 	public long getBlocktime() {
    40. 		return blocktime;
    41. 	}
    43. 	public void setBlocktime(long blocktime) {
    44. 		this.blocktime = blocktime;
    45. 	}

    46. //  运行的三个状态
    47. 	public final static String STATE_READY = "READY";
    48. 	public final static String STATE_RUN = "RUN";
    49. 	public final static String STATE_BLOCK = "BLOCK";

    51. 	
    52. 	
    53. 	public long getId() {
    54. 		return id;
    55. 	}
    57. 	public void setId(long id) {
    58. 		this.id = id;
    59. 	}
    61. 	public int getPriority() {
    62. 		return priority;
    63. 	}
    65. 	public void setPriority(int priority) {
    66. 		this.priority = priority;
    67. 	}
    69. 	public long getCputime() {
    70. 		return cputime;
    71. 	}
    73. 	public void setCputime(long cputime) {
    74. 		this.cputime = cputime;
    75. 	}
    77. 	public long getAlltime() {
    78. 		return alltime;
    79. 	}
    81. 	public void setAlltime(long alltime) {
    82. 		this.alltime = alltime;
    83. 	}
    85. 	public long getStartblock() {
    86. 		return startblock;
    87. 	}
    89. 	public void setStartblock(long startblock) {
    90. 		this.startblock = startblock;
    91. 	}
    93. }
    好了，现在是主要的线程调度算法，注意优先级的调整：
    1. import java.util.ArrayList;
    2. import java.util.Arrays;
    3. import java.util.Comparator;
    4. import java.util.Iterator;
    5. import java.util.List;
    7. public class OrderImitate {
    8. 	
    9. //  按优先级次序排列的数组
    10. 	private ArrayList<PCB> priorityArrayList = null;
    11. 	
    12. 	
    13. /**
    14.  * 	优先级排序
    15.  */
    16. 	public void sortArray(){
    17. 		PCB[] pcbs = (PCB[])priorityArrayList.toArray(new PCB[priorityArrayList.size()]);
    18. 		Arrays.sort(pcbs, new MyComprator());
    19. 		List<PCB> list = Arrays.asList(pcbs);
    20. 		this.priorityArrayList = new ArrayList<PCB>(list);
    21. 	}
    22. 	
    23. /**
    24.  * 	初始化，按照书中的数据进行初始化操作
    25.  */
    26. 	private void init(){
    27. 		priorityArrayList = new ArrayList<PCB>();
    28. 		PCB zero = new PCB(0, 9, 0, 3, 2, 3, PCB.STATE_READY);
    29. 		priorityArrayList.add(zero);
    30. 		
    31. 		PCB one = new PCB(1, 38, 0, 3, -1, 0, PCB.STATE_READY);
    32. 		priorityArrayList.add(one);
    33. 		
    34. 		PCB two = new PCB(2, 30, 0, 6, -1, 0, PCB.STATE_READY);
    35. 		priorityArrayList.add(two);
    36. 		
    37. 		PCB three = new PCB(3, 29, 0, 3, -1, 0, PCB.STATE_READY);
    38. 		priorityArrayList.add(three);
    39. 		
    40. 		PCB four = new PCB(4, 0, 0, 4, -1, 0, PCB.STATE_READY);
    41. 		priorityArrayList.add(four);
    42. 		
    43. 		sortArray();
    44. 	}
    45. 	
    46. 	
    47. /**
    48.  * 优先级执行算法
    49.  * @return
    50.  */
    51. 	public boolean hightpPriority(){
    52. 		
    53. //		获得第一个元素
    54. 		PCB first = priorityArrayList.get(0);
    55. 		
    56. 		if(!first.getState().equals(PCB.STATE_BLOCK)){
    57. //			运行一次优先级顺序-3
    58. 			first.setPriority(first.getPriority()-3);
    59. 			first.setCputime(first.getCputime()+1);
    60. 			first.setAlltime(first.getAlltime()-1);
    61. //			是否进入阻塞状态
    62. 			if(first.getStartblock() > 0){
    63. 				first.setStartblock(first.getStartblock() - 1);
    64. 			}
    65. //			当是阻塞状态的时候，将状态变为阻塞
    66. 			if(first.getStartblock() == 0){
    67. 				first.setState(PCB.STATE_BLOCK);
    68. 			}
    69. 		}
    70. 		
    71. //		所需要的时间片完成，结束运行
    72. 		if(first.getAlltime() == 0){
    73. 			System.out.println("----------------------------------------------");
    74. 			System.out.println("ID " + first.getId() + " have done !");
    75. 			System.out.println("----------------------------------------------");
    76. 			priorityArrayList.remove(0);
    77. 		}
    78. 		
    79. //		后面的任务优先级+1
    80. 		Iterator<PCB> iterator = priorityArrayList.iterator();
    81. 		int count = 0;
    82. 		while(iterator.hasNext()){
    83. 			if(count == 0){
    84. 				count++;
    85. 				iterator.next();
    86. 				continue;
    87. 			}
    88. 			PCB pcb = iterator.next();
    89. 			pcb.setPriority(pcb.getPriority()+1);
    90. //			PCB的阻塞状态改变
    91. 			if(pcb.getBlocktime() != 0 && pcb.getState().equals(PCB.STATE_BLOCK)){
    92. 				pcb.setBlocktime(pcb.getBlocktime() -1);
    93. 				if(pcb.getBlocktime() == 0){
    94. 					pcb.setState(PCB.STATE_READY);
    95. 				}
    96. 			}
    97. 		}
    98. 		
    99. 		sortArray();
    100. 		
    101. 		return true;
    102. 	}
    103. 	
    104. 	/**
    105. 	 * 执行程序
    106. 	 */
    107. 	public void startRuning(){
    108. 		while(hightpPriority()){
    109. 			if(this.priorityArrayList.size() == 0){
    110. 				System.out.println("-----------------> ALL Works have done !");
    111. 				break;
    112. 			}
    113. //			输出数据
    114. 			Iterator<PCB> iterator = priorityArrayList.iterator();
    115. 			System.out.println("-----------------------------------------------------------------------------------------");
    116. 			System.out.println("ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE");
    117. 			while(iterator.hasNext()){
    118. 				PCB pcb = iterator.next();
    119. 				System.out
    120. 						.printf("%d %8d %12d %12d %13d %14d %18s
", pcb.getId(),
    121. 								pcb.getPriority(), pcb.getCputime(),
    122. 								pcb.getAlltime(), pcb.getStartblock(),
    123. 								pcb.getBlocktime(), pcb.getState());
    124. 			}
    125. 			System.out.println("-----------------------------------------------------------------------------------------");
    126. 		}
    127. 	}
    128. 	
    129. 	public static void main(String[] args) {
    130. 		OrderImitate orderImitate = new OrderImitate();
    131. 		orderImitate.init();
    132. 		orderImitate.startRuning();
    133. 	}
    134. 	
    135. //	优先级次序调整，优先级高且没有阻塞的进程在前面
    136. 	class MyComprator implements Comparator<PCB> {
    137. 	    public int compare(PCB o1, PCB o2) {
    138. 	    	
    139. 			if((o1.getState().equals(PCB.STATE_READY) && o2.getState().equals(PCB.STATE_READY)) || (o1.getState().equals(PCB.STATE_BLOCK) && o2.getState().equals(PCB.STATE_BLOCK))){
    140. 				if(o1.getPriority() == o2.getPriority() ){
    141. 					return 0;
    142. 				}
    143. 				else if(o1.getPriority() > o2.getPriority()){
    144. 					return -1;
    145. 				}else {
    146. 					return 1;
    147. 				}
    148. 			}else if(o1.getState().equals(PCB.STATE_BLOCK) && o2.getState().equals(PCB.STATE_READY)){
    149. 				return 1;
    150. 			}else{
    151. 				return -1; 
    152. 			}
    153. 			
    154. 		}
    155. 	}
    156. 	
    157. }
    一开始是想用优先队列的，但是碰上个问题，如果有多个线程同时进入阻塞状态，那么就可能第二个到后面那个都无法运行，这样没有完全排好序的优先队列就没有办法使用了，而且优先队列碰上一个大的问题，不知道什么，中途修改了队列中的值没有触发队列的排序，导致后面的一系列次序无法进行。


    好的，现在看看最后的结果：
    1. -----------------------------------------------------------------------------------------
    2. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    3. 1       35            1            2            -1              0              READY
    4. 2       31            0            6            -1              0              READY
    5. 3       30            0            3            -1              0              READY
    6. 0       10            0            3             2              3              READY
    7. 4        1            0            4            -1              0              READY
    8. -----------------------------------------------------------------------------------------
    9. -----------------------------------------------------------------------------------------
    10. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    11. 1       32            2            1            -1              0              READY
    12. 2       32            0            6            -1              0              READY
    13. 3       31            0            3            -1              0              READY
    14. 0       11            0            3             2              3              READY
    15. 4        2            0            4            -1              0              READY
    16. -----------------------------------------------------------------------------------------
    17. ----------------------------------------------
    18. ID 1 have done !
    19. ----------------------------------------------
    20. -----------------------------------------------------------------------------------------
    21. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    22. 2       32            0            6            -1              0              READY
    23. 3       32            0            3            -1              0              READY
    24. 0       12            0            3             2              3              READY
    25. 4        3            0            4            -1              0              READY
    26. -----------------------------------------------------------------------------------------
    27. -----------------------------------------------------------------------------------------
    28. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    29. 3       33            0            3            -1              0              READY
    30. 2       29            1            5            -1              0              READY
    31. 0       13            0            3             2              3              READY
    32. 4        4            0            4            -1              0              READY
    33. -----------------------------------------------------------------------------------------
    34. -----------------------------------------------------------------------------------------
    35. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    36. 3       30            1            2            -1              0              READY
    37. 2       30            1            5            -1              0              READY
    38. 0       14            0            3             2              3              READY
    39. 4        5            0            4            -1              0              READY
    40. -----------------------------------------------------------------------------------------
    41. -----------------------------------------------------------------------------------------
    42. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    43. 2       31            1            5            -1              0              READY
    44. 3       27            2            1            -1              0              READY
    45. 0       15            0            3             2              3              READY
    46. 4        6            0            4            -1              0              READY
    47. -----------------------------------------------------------------------------------------
    48. -----------------------------------------------------------------------------------------
    49. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    50. 2       28            2            4            -1              0              READY
    51. 3       28            2            1            -1              0              READY
    52. 0       16            0            3             2              3              READY
    53. 4        7            0            4            -1              0              READY
    54. -----------------------------------------------------------------------------------------
    55. -----------------------------------------------------------------------------------------
    56. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    57. 3       29            2            1            -1              0              READY
    58. 2       25            3            3            -1              0              READY
    59. 0       17            0            3             2              3              READY
    60. 4        8            0            4            -1              0              READY
    61. -----------------------------------------------------------------------------------------
    62. ----------------------------------------------
    63. ID 3 have done !
    64. ----------------------------------------------
    65. -----------------------------------------------------------------------------------------
    66. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    67. 2       25            3            3            -1              0              READY
    68. 0       18            0            3             2              3              READY
    69. 4        9            0            4            -1              0              READY
    70. -----------------------------------------------------------------------------------------
    71. -----------------------------------------------------------------------------------------
    72. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    73. 2       22            4            2            -1              0              READY
    74. 0       19            0            3             2              3              READY
    75. 4       10            0            4            -1              0              READY
    76. -----------------------------------------------------------------------------------------
    77. -----------------------------------------------------------------------------------------
    78. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    79. 0       20            0            3             2              3              READY
    80. 2       19            5            1            -1              0              READY
    81. 4       11            0            4            -1              0              READY
    82. -----------------------------------------------------------------------------------------
    83. -----------------------------------------------------------------------------------------
    84. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    85. 2       20            5            1            -1              0              READY
    86. 0       17            1            2             1              3              READY
    87. 4       12            0            4            -1              0              READY
    88. -----------------------------------------------------------------------------------------
    89. ----------------------------------------------
    90. ID 2 have done !
    91. ----------------------------------------------
    92. -----------------------------------------------------------------------------------------
    93. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    94. 0       17            1            2             1              3              READY
    95. 4       13            0            4            -1              0              READY
    96. -----------------------------------------------------------------------------------------
    97. -----------------------------------------------------------------------------------------
    98. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    99. 4       14            0            4            -1              0              READY
    100. 0       14            2            1             0              3              BLOCK
    101. -----------------------------------------------------------------------------------------
    102. 可以看到这里因为线程阻塞产生了调度：
    103. -----------------------------------------------------------------------------------------
    104. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    105. 4       11            1            3            -1              0              READY
    106. 0       15            2            1             0              2              BLOCK
    107. -----------------------------------------------------------------------------------------
    108. -----------------------------------------------------------------------------------------
    109. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    110. 4        8            2            2            -1              0              READY
    111. 0       16            2            1             0              1              BLOCK
    112. -----------------------------------------------------------------------------------------
    113. -----------------------------------------------------------------------------------------
    114. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    115. 0       17            2            1             0              0              READY
    116. 4        5            3            1            -1              0              READY
    117. -----------------------------------------------------------------------------------------
    118. ----------------------------------------------
    119. ID 0 have done !
    120. ----------------------------------------------
    121. -----------------------------------------------------------------------------------------
    122. ID      PRIORITY      CPUTIME      ALLTIME      STARTBLOCK      BLOCKTIME      STATE
    123. 4        5            3            1            -1              0              READY
    124. -----------------------------------------------------------------------------------------
    125. ----------------------------------------------
    126. ID 4 have done !
    127. ----------------------------------------------
    128. -----------------> ALL Works have done !
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  • 原文地址：https://www.cnblogs.com/sober-reflection/p/4192315.html
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