ch6.htm

汤子瀛《操作系统》电子教案

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    <p style="TEXT-ALIGN: center" align="center"><font color="#FFFFFF"><a name="ch62"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"></span></a><span lang="EN-US" style="mso-bidi-font-size: 10.0pt">6</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt">2<span style="mso-spacerun: yes">&nbsp;   
    </span></span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">请求页式存储管理方式</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
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    <p style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; mso-list: l10 level1 lfo15; tab-stops: list 18.0pt"><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">请求分页中的硬件支持</span></font></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑴页表机制</font></span></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑵缺页中断机构</font></span></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑶地址变换机构</font></span></p>
    <p style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; mso-list: l10 level1 lfo15; tab-stops: list 18.0pt"><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">页面分配</span></font></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑴最小物理块数</font></span></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑵页面分配和置换策略</font></span></p>
    <p style="MARGIN-LEFT: 36pt; TEXT-INDENT: -12pt; mso-list: l6 level1 lfo16; tab-stops: list 36.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">①</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">固定分配局部置换</span></font></p>
    <p style="MARGIN-LEFT: 36pt; TEXT-INDENT: -12pt; mso-list: l6 level1 lfo16; tab-stops: list 36.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">②</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">可变分配全局置换</span></font></p>
    <p style="MARGIN-LEFT: 24pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">③可变分配局部置换</font></span></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑶分配算法</font></span></p>
    <p style="MARGIN-LEFT: 36pt; TEXT-INDENT: -12pt; mso-list: l12 level1 lfo17; tab-stops: list 36.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">①</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">平均分配算法</span></font></p>
    <p style="MARGIN-LEFT: 36pt; TEXT-INDENT: -12pt; mso-list: l12 level1 lfo17; tab-stops: list 36.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">②</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">按比例分配算法</span></font></p>
    <p style="MARGIN-LEFT: 36pt; TEXT-INDENT: -12pt; mso-list: l12 level1 lfo17; tab-stops: list 36.0pt"><font color="#FFFFFF"><span lang="EN-US" style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">③</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">考虑优先权的分配算法</span></font></p>
    <p style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; mso-list: l10 level1 lfo15; tab-stops: list 18.0pt"><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">页面调入策略</span></font></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑴何时调入页面</font></span></p>
    <p style="MARGIN-LEFT: 18pt"><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
    </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">预掉页策略、请求调页策略</span></font></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑵从何调入页面</font></span></p>
    <p style="MARGIN-LEFT: 18pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">⑶页面调入过程</font></span></p>
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      <p style="TEXT-ALIGN: center" align="center"><font color="#FFFFFF"><a name="ch63"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"></span></a><span lang="EN-US" style="mso-bidi-font-size: 10.0pt">6</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt">3<span style="mso-spacerun: yes">&nbsp;   
      </span></span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">页面置换算法</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
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      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">抖动现象</span></font></p>
      <p style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; mso-list: l14 level1 lfo18; tab-stops: list 18.0pt"><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">最佳置换算法（理想置换算法）</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑴算法：淘汰永不使用的或是在最长时间内不再被访问的页</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑵无实现价值，作为其它算法的衡量标准</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">．先进现出置换算法：</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑴算法：淘汰最先进出主存的页</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑵性能差、有异常现象（</span><span lang="EN-US">belady</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">现象）</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">举例：设进程有</span><span lang="EN-US">5</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">页，访问顺序：</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">，</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">5</span><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">，</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">，</span><span lang="EN-US">5</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">，分</span><span lang="EN-US">3</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">块主存块和</span><span lang="EN-US">4</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">块主存块时。</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">．最近最久未使用（</span><span lang="EN-US">LRU</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）算法</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑴算法：淘汰最近最久未使用的页</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑵硬件支持（实现方法）</span></font></p>
      <p style="TEXT-INDENT: 24pt"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><font color="#FFFFFF">寄存器、栈</font></span></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑶特点：软件实现：系统“非生产性”开销过大；</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">硬件实现：增大成本</span></font></p>
      <p style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; mso-list: l10 level1 lfo15; tab-stops: list 18.0pt"><font color="#FFFFFF"><span lang="EN-US">4．Clock</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">置换算法（</span><span lang="EN-US">LRU</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">算法的近似实现）</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">　⑴简单的</span><span lang="EN-US">Clock</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">置换算法</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑵改进型</span><span lang="EN-US">Clock</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">置换算法</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">5</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．最少使用（</span><span lang="EN-US">LFU</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">）置换算法</span></font></p>
      <p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US">&nbsp;&nbsp;   
      </span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">淘汰最近使用次数最少的页</span></font></p>
      <p><font color="#FFFFFF"><span lang="EN-US">6</span><span style="mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">．页面缓冲置换算法</span></font></p>
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