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15.5 线程的优先级
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15.5 线程的优先级
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2006-10-13 14:41:00
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<div style='float:left;width:49%'>·<a href='100165450.htm'>15.2 多线程应用程序</a></div><div style='float:right;width:49%'>·<a href='100165451.htm'>15.3 线程的处理</a></div><div style='float:left;width:49%'>·<a href='100165452.htm'>15.4 ThreadPlayaround示例</a></div><div style='float:right;width:49%'>·<a href='100165454.htm'>15.6 同步</a></div><div style='float:left;width:49%'>·<a href='100165455.htm'>15.6.1 同步的含义</a></div><div style='float:right;width:49%'>·<a href='100165456.htm'>15.6.2 同步问题</a></div></div>
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<div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><h3 style="MARGIN-TOP: 11.4pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 11.4pt"><a ftel="_Toc507815088"><span lang="EN-US">15.5 </span></a><span style="FONT-FAMILY: 楷体_GB2312">线程的优先级</span></h3>
<p class="MsoNormal"><a ftel="priorities"><span style="FONT-FAMILY: 宋体">如果在应用程序中有多个线程在运行，但一些线程比另一些线程重要，该怎么办？在这种情况下，可以在一个进程中为不同的线程指定不同的优先级。一般情况下，如果有优先级较高的线程在工作，就不会给优先级较低的线程分配任何时间片，其优点是可以保证给接收用户输入的线程指定较高的优先级。在大多数的时间内，这个线程什么也不做，而其他线程则执行它们的任务。但是，如果用户输入了信息，这个线程就立即获得比应用程序中其他线程更高的优先级，在短时间内处理用户输入事件。</span></a></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">高优先级的线程可以完全阻止低优先级的线程执行，因此在改变线程的优先级时要特别小心。线程的优先级可以定义为</span><span lang="EN-US">ThreadPriority</span><span style="FONT-FAMILY: 宋体">枚举的值，即</span><span lang="EN-US">Highest</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">AboveNormal</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Normal</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">BelowNormal</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US"> Lowest</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">注意，每个进程都有一个基本优先级，这些值与进程的优先级是有关系的。给线程指定较高的优先级，可以确保它在该进程中比其他线程优先执行，但系统上可能还运行着其他进程，它们的线程有更高的优先级。因此</span><span lang="EN-US">Windows</span><span style="FONT-FAMILY: 宋体">给自己的操作系统线程指定高优先级。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在</span><span lang="EN-US">ThreadPlayaround</span><span style="FONT-FAMILY: 宋体">示例中，对</span><span lang="EN-US">Main()</span><span style="FONT-FAMILY: 宋体">方法做如下修改，就可以看出修改线程的优先级的效果：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US"> ThreadStart workerStart = new ThreadStart(StartMethod);</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> Thread workerThread = new Thread(workerStart);</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> workerThread.Name = "Worker";</span></p>
<p class="2" style="MARGIN-TOP: 6pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US"> workerThread.Priority = ThreadPriority.AboveNormal;</span></p>
<p class="a6" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US"> workerThread.Start();</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">其中，工作线程的优先级比主线程高，运行结果如下所示：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><strong><span lang="EN-US">ThreadPlayaroundWithPriorities</span></strong></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Interval to display results at?> <strong>1000000</strong></span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Starting thread: Main Thread</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: Current Culture = en-US</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Starting thread: Worker</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: Current Culture = en-US</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 1000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 1000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 2000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 3000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 4000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 5000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 6000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 7000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker: count has reached 8000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Worker Thread Finished</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 2000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 3000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 4000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 5000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 6000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 7000000</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Main Thread: count has reached 8000000</span></p>
<p class="a6" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Main Thread Finished</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">这<span style="LETTER-SPACING: -0.1pt">说明，当工作线程的优先级为</span></span><span lang="EN-US" style="LETTER-SPACING: -0.1pt">AboveNormal</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.1pt">时，一旦工作线程被启动，主线程就不再运行。</span></p></div>
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<div style='float:left;width:49%'>·<a href='100165450.htm'>15.2 多线程应用程序</a></div><div style='float:right;width:49%'>·<a href='100165451.htm'>15.3 线程的处理</a></div><div style='float:left;width:49%'>·<a href='100165452.htm'>15.4 ThreadPlayaround示例</a></div><div style='float:right;width:49%'>·<a href='100165454.htm'>15.6 同步</a></div><div style='float:left;width:49%'>·<a href='100165455.htm'>15.6.1 同步的含义</a></div><div style='float:right;width:49%'>·<a href='100165456.htm'>15.6.2 同步问题</a></div></div>
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