ch4.htm

汤子瀛《操作系统》电子教案

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            <p style="TEXT-ALIGN: center" align="center"><span lang="EN-US"><font color="#FFFFFF">2.1</font></span></p>
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    <p><span lang="EN-US"><font color="#FFFFFF">&nbsp;<o:p>
    </o:p>
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    <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．2．2 
    短作业（进程）优先调度算法</font></span></p>
    <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．2．3 
    时间片轮转调度算法</font></span></p>
    <p style="MARGIN-LEFT: 24pt; TEXT-INDENT: -24pt; mso-list: l11 level1 lfo32; tab-stops: list 24.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman">一、</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman">调度算法</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt; mso-fareast-font-family: 黑体"><o:p>
    </o:p>
    </span></font></p>
    <p style="MARGIN-LEFT: 24pt; TEXT-INDENT: -24pt; mso-list: l11 level1 lfo32; tab-stops: list 24.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman">二、</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman">时间片大小的确定</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt; mso-fareast-font-family: 黑体"><o:p>
    </o:p>
    </span></font></p>
    <p style="MARGIN-LEFT: 15.75pt; TEXT-INDENT: -15.75pt; mso-list: l10 level1 lfo20; tab-stops: list 15.75pt"><font color="#FFFFFF"><span lang="EN-US">1．</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">系统对响应时间的要求</span></font></p>
    <p style="MARGIN-LEFT: 15.75pt; TEXT-INDENT: -15.75pt; mso-list: l10 level1 lfo20; tab-stops: list 15.75pt"><font color="#FFFFFF"><span lang="EN-US">2．</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">就绪队列中进程的数目</span></font></p>
    <p style="MARGIN-LEFT: 15.75pt; TEXT-INDENT: -15.75pt; mso-list: l10 level1 lfo20; tab-stops: list 15.75pt"><font color="#FFFFFF"><span lang="EN-US">3．</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">系统的处理能力</span></font></p>
    <p><span lang="EN-US"><font color="#FFFFFF">&nbsp;<o:p>
    </o:p>
    </font></span></p>
    <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．2．4 
    优先权调度算法</font></span></p>
    <p style="MARGIN-LEFT: 21pt; TEXT-INDENT: -21pt; mso-list: l13 level1 lfo19; tab-stops: list 21.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">一、</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">优先权调度算法的类型</span></font></p>
    <p><font color="#FFFFFF"><span lang="EN-US">1</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．非抢占式优先权算法</span></font></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">主要用于批处理系统中；也可用于某些对实时性要求不严的实时系统中。</font></span></p>
    <p><font color="#FFFFFF"><span lang="EN-US">2</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．抢占式优先权调度算法</span></font></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">这种方式的优先权调度算法．能更好地满足紧迫作业的要求，常用于要求比较严格的实时系统中，以及对性能要求较高的批处理和分时系统中。</font></span></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">二、优先权的类型</font></span></p>
    <p style="MARGIN-LEFT: 15.75pt; TEXT-INDENT: -15.75pt; mso-list: l22 level1 lfo21; tab-stops: list 15.75pt"><font color="#FFFFFF"><span lang="EN-US">1．</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">静态优先权</span></font></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">在创建进程时确定，且优先权在整个进程的生命周期内不会发生变化。</font></span></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">确定优先权的依据有：</font></span></p>
    <p><font color="#FFFFFF"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">（</span><span lang="EN-US">1</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）进程类型。（</span><span lang="EN-US">2</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）进程对资源的需求。（</span><span lang="EN-US">3</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）根据用户要求。</span></font></p>
    <p><font color="#FFFFFF"><span lang="EN-US">2</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．动态优先权</span></font></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">在创建进程时所赋予的优先权，可以随进程的推进而改变，以便获得更好的调度性能。</font></span></p>
    <p><span lang="EN-US"><font color="#FFFFFF">&nbsp;<o:p>
    </o:p>
    </font></span></p>
    <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．2．5 
    高响应比优先调度算法</font></span></p>
    <p><span style="mso-spacerun: yes" lang="EN-US"><font color="#FFFFFF">&nbsp;</font></span></p>
    <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．2．6 
    多级队列调度</font></span></p>
    <p><span lang="EN-US"><font color="#FFFFFF">&nbsp;<o:p>
    </o:p>
    </font></span></p>
    <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．2．7 
    多级反馈队列调度算法</font></span></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">一、调度算法</font></span></p>
    <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">二、多绍反馈队列调度算法的牲能</font></span></p>
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      <p style="TEXT-ALIGN: center" align="center"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF"><a name="ch43"></a>4．3<span style="mso-spacerun: yes">&nbsp; 
      </span>实时系统中的调度<o:p>
      </o:p>
      </font></span></p>
      <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．3．1<span style="mso-spacerun: yes">&nbsp; 
      </span>对实时系统的要求<o:p>
      </o:p>
      </font></span></p>
      <p style="MARGIN-LEFT: 15.75pt; TEXT-INDENT: -15.75pt; mso-list: l23 level1 lfo23; tab-stops: list 15.75pt"><font color="#FFFFFF"><span lang="EN-US">1．</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">提供必要的调度信息</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">（</span><span lang="EN-US">1</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）就绪时间。（</span><span lang="EN-US">2</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）开始截止时间和完成截止时间。（</span><span lang="EN-US">3</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）处理时间。（</span><span lang="EN-US">4</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）资源要求。（</span><span lang="EN-US">5</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）优先级。</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">2</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．调度方式</span></font></p>
      <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">在实时控制系统中，广泛采用抢占调度方式。</font></span></p>
      <p><font color="#FFFFFF"><span lang="EN-US">3</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．具有快速响应外部中断的能力</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">4</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．快速任务分派</span></font></p>
      <p><span lang="EN-US"><font color="#FFFFFF">&nbsp;<o:p>
      </o:p>
      </font></span></p>
      <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．3．2<span style="mso-spacerun: yes">&nbsp; 
      </span>实时调度算法<o:p>
      </o:p>
      </font></span></p>
      <p><font color="#FFFFFF"><span lang="EN-US">1</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．时间片轮转调度算法</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">2</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．非抢占优先权调度算法</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">3</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．基于时钟中断抢占的优先权调度算法</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">4</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．立即抢占的优先权调度</span></font></p>
      <p><span lang="EN-US"><font color="#FFFFFF">&nbsp;<o:p>
      </o:p>
      </font></span></p>
      <p><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF">4．3．3<span style="mso-spacerun: yes">&nbsp; 
      </span>实时调度实例<o:p>
      </o:p>
      </font></span></p>
      <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">一、具有开始截止时间的非周期实时任务的调度</font></span></p>
      <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">在事前能知道各实时任务的开始截止时间，且对调度时延要求不太严格的情况下，系统采用最早截止时间优先的非剥夺调度策略。</font></span></p>
      <p><font color="#FFFFFF"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">任务</span><span lang="EN-US">1</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">、</span><span lang="EN-US">2</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">、</span><span lang="EN-US">3</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">、</span><span lang="EN-US">4</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">的调度</span></font></p>
      <p><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">二、具有完成截止时间的周期性实时任务的调度</font></span></p>
      <p><font color="#FFFFFF"><span lang="EN-US">A</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">：每</span><span lang="EN-US">20ms</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">执行一次，执行时间为</span><span lang="EN-US">10ms</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">。</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">B</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">：每</span><span lang="EN-US">50ms</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">执行一次，执行时间为</span><span lang="EN-US">25ms</span></font></p>
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      <p style="TEXT-ALIGN: center" align="center"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF"><a name="ch44"></a>4．4<span style="mso-spacerun: yes">&nbsp; 
      </span>多处理机调度<o:p>
      </o:p>
      </font></span></p>