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<?xml version="1.0" encoding="gb2312"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312"/><title>linux for ppc chapter 15               jacobw </title></head><body><center><h1>BBS 水木清华站∶精华区</h1></center><a name="top"></a>发信人:&nbsp;plato&nbsp;(纯真年代),&nbsp;信区:&nbsp;Embedded&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br />标&nbsp;&nbsp;题:&nbsp;linux&nbsp;for&nbsp;ppc&nbsp;chapter&nbsp;15&nbsp;<br />发信站:&nbsp;BBS&nbsp;水木清华站&nbsp;(Wed&nbsp;May&nbsp;30&nbsp;23:21:04&nbsp;2001)&nbsp;<br />&nbsp;<br />Next&nbsp;Previous&nbsp;Contents&nbsp;<br />----------------------------------------------------------------------------&nbsp;<br />----&nbsp;<br />15.&nbsp;Real&nbsp;Time&nbsp;Response&nbsp;<br />Check&nbsp;out&nbsp;MontaVista's&nbsp;Linux&nbsp;Real-Time&nbsp;characterisation&nbsp;projects&nbsp;at&nbsp;<a href="http://w">http://w</a>&nbsp;<br />ww.mvista.com/realtime&nbsp;<br />15.1&nbsp;Soft&nbsp;<br />For&nbsp;many&nbsp;applications&nbsp;a&nbsp;soft&nbsp;real&nbsp;time&nbsp;user&nbsp;space&nbsp;thread&nbsp;is&nbsp;adequate,&nbsp;partic&nbsp;<br />ularly&nbsp;if&nbsp;you&nbsp;minimise&nbsp;kernel&nbsp;scheduling&nbsp;latency&nbsp;with&nbsp;the&nbsp;patches&nbsp;at:&nbsp;http:/&nbsp;<br />/www.redhat.com/~mingo/lowlatency-patches/&nbsp;<br />Also,&nbsp;see:&nbsp;<a href="http://lists.linuxppc.org/listarcs/linuxppc-embedded/199912/msg00">http://lists.linuxppc.org/listarcs/linuxppc-embedded/199912/msg00</a>&nbsp;<br />006.html&nbsp;<br />15.2&nbsp;Hard&nbsp;<br />If&nbsp;your&nbsp;application&nbsp;requires&nbsp;a&nbsp;hard&nbsp;real&nbsp;time&nbsp;response&nbsp;with&nbsp;guaranteed&nbsp;low&nbsp;l&nbsp;<br />atency,&nbsp;you&nbsp;may&nbsp;need&nbsp;to&nbsp;encapsulate&nbsp;the&nbsp;real&nbsp;time&nbsp;aspects&nbsp;in&nbsp;a&nbsp;device&nbsp;driver&nbsp;<br />.&nbsp;This&nbsp;is&nbsp;how&nbsp;devices&nbsp;which&nbsp;have&nbsp;real&nbsp;time&nbsp;constraints&nbsp;such&nbsp;as&nbsp;serial&nbsp;ports&nbsp;&nbsp;<br />and&nbsp;disk&nbsp;drives&nbsp;are&nbsp;traditionally&nbsp;handled&nbsp;under&nbsp;most&nbsp;non-realtime&nbsp;operating&nbsp;&nbsp;<br />systems,&nbsp;including&nbsp;Linux.&nbsp;<br />Interrupt&nbsp;Latency&nbsp;<br />The&nbsp;real-time&nbsp;response&nbsp;of&nbsp;a&nbsp;driver&nbsp;will&nbsp;still&nbsp;be&nbsp;affected&nbsp;by&nbsp;other&nbsp;kernel&nbsp;co&nbsp;<br />de&nbsp;which&nbsp;may&nbsp;disable&nbsp;interrupts&nbsp;for&nbsp;unknown&nbsp;periods,&nbsp;increasing&nbsp;effective&nbsp;in&nbsp;<br />terrupt&nbsp;latency.&nbsp;For&nbsp;some&nbsp;tools&nbsp;to&nbsp;help&nbsp;measure&nbsp;interrupt&nbsp;latency,&nbsp;see:&nbsp;http&nbsp;<br />∶<i>//www.drfruitcake.com/linux/irq_blk.html&nbsp;</i><br />RTLinux&nbsp;-&nbsp;Real&nbsp;Time&nbsp;Linux&nbsp;<br /><a href="http://www.rtlinux.com/">http://www.rtlinux.com/</a>&nbsp;<br />If&nbsp;you&nbsp;need&nbsp;better&nbsp;latency&nbsp;guarantees&nbsp;than&nbsp;offerred&nbsp;by&nbsp;the&nbsp;kernel,&nbsp;use&nbsp;Real&nbsp;&nbsp;<br />Time&nbsp;Linux&nbsp;to&nbsp;decouple&nbsp;the&nbsp;hard&nbsp;real&nbsp;time&nbsp;portion&nbsp;from&nbsp;the&nbsp;rest&nbsp;of&nbsp;your&nbsp;appl&nbsp;<br />ication.&nbsp;v3.0&nbsp;includes&nbsp;support&nbsp;for&nbsp;PowerPC.&nbsp;<br />Also,&nbsp;search&nbsp;for&nbsp;RTLinux.&nbsp;<br />RTAI&nbsp;-&nbsp;Real&nbsp;Time&nbsp;Application&nbsp;Interface&nbsp;<br /><a href="http://www.aero.polimi.it/projects/rtai/">http://www.aero.polimi.it/projects/rtai/</a>&nbsp;<br />The&nbsp;Real&nbsp;Time&nbsp;Application&nbsp;Interface&nbsp;is&nbsp;a&nbsp;kernel&nbsp;module&nbsp;which&nbsp;uses&nbsp;a&nbsp;hardware&nbsp;<br />&nbsp;abstraction&nbsp;layer&nbsp;to&nbsp;add&nbsp;typical&nbsp;features&nbsp;from&nbsp;an&nbsp;industrial&nbsp;real&nbsp;time&nbsp;oper&nbsp;<br />ating&nbsp;system&nbsp;to&nbsp;Linux.&nbsp;It&nbsp;consists&nbsp;basically&nbsp;of&nbsp;an&nbsp;interrupt&nbsp;dispatcher&nbsp;and&nbsp;&nbsp;<br />mainly&nbsp;traps&nbsp;the&nbsp;peripherals&nbsp;interrupts&nbsp;and&nbsp;if&nbsp;necessary&nbsp;re-routes&nbsp;them&nbsp;to&nbsp;L&nbsp;<br />inux.&nbsp;<br />RTAI&nbsp;is&nbsp;supported&nbsp;on&nbsp;a&nbsp;number&nbsp;of&nbsp;MPC8xx&nbsp;systems&nbsp;by&nbsp;people&nbsp;like&nbsp;Denx.&nbsp;<br />----------------------------------------------------------------------------&nbsp;<br />----&nbsp;<br />Next&nbsp;Previous&nbsp;Contents&nbsp;&nbsp;<br />&nbsp;<br />--&nbsp;<br />&nbsp;<br />※&nbsp;来源:·BBS&nbsp;水木清华站&nbsp;smth.org·[FROM:&nbsp;166.111.161.8]&nbsp;<br /><a href="00000015.htm">上一篇</a><a href="javascript:history.go(-1)">返回上一页</a><a href="index.htm">回到目录</a><a href="#top">回到页首</a><a href="00000017.htm">下一篇</a></h1></center><center><h1>BBS 水木清华站∶精华区</h1></center></body></html>
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