ceph/src/boost/libs/fiber/doc/html/fiber/integration/embedded_main_loop.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   4 <title>Embedded Main Loop</title>
   5 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
   6 <meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
   7 <link rel="home" href="../../index.html" title="Chapter&#160;1.&#160;Fiber">
   8 <link rel="up" href="../integration.html" title="Sharing a Thread with Another Main Loop">
   9 <link rel="prev" href="event_driven_program.html" title="Event-Driven Program">
  10 <link rel="next" href="deeper_dive_into___boost_asio__.html" title="Deeper Dive into Boost.Asio">
  11 </head>
  12 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  13 <table cellpadding="2" width="100%"><tr>
  14 <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
  15 <td align="center"><a href="../../../../../../index.html">Home</a></td>
  16 <td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
  17 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  18 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  19 <td align="center"><a href="../../../../../../more/index.htm">More</a></td>
  20 </tr></table>
  21 <hr>
  22 <div class="spirit-nav">
  23 <a accesskey="p" href="event_driven_program.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../integration.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="deeper_dive_into___boost_asio__.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
  24 </div>
  25 <div class="section">
  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="fiber.integration.embedded_main_loop"></a><a name="embedded_main_loop"></a><a class="link" href="embedded_main_loop.html" title="Embedded Main Loop">Embedded
  28       Main Loop</a>
  29 </h3></div></div></div>
  30 <p>
  31         More challenging is when the application&#8217;s main loop is embedded in some other
  32         library or framework. Such an application will typically, after performing
  33         all necessary setup, pass control to some form of <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code> function from which control does not return
  34         until application shutdown.
  35       </p>
  36 <p>
  37         A <a href="http://www.boost.org/doc/libs/release/libs/asio/index.html" target="_top">Boost.Asio</a>
  38         program might call <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/io_service/run.html" target="_top"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">run</span><span class="special">()</span></code></a>
  39         in this way.
  40       </p>
  41 <p>
  42         In general, the trick is to arrange to pass control to <a class="link" href="../fiber_mgmt/this_fiber.html#this_fiber_yield"><code class="computeroutput">this_fiber::yield()</code></a> frequently.
  43         You could use an <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/high_resolution_timer.html" target="_top">Asio
  44         timer</a> for that purpose. You could instantiate the timer, arranging
  45         to call a handler function when the timer expires. The handler function could
  46         call <code class="computeroutput"><span class="identifier">yield</span><span class="special">()</span></code>,
  47         then reset the timer and arrange to wake up again on its next expiration.
  48       </p>
  49 <p>
  50         Since, in this thought experiment, we always pass control to the fiber manager
  51         via <code class="computeroutput"><span class="identifier">yield</span><span class="special">()</span></code>,
  52         the calling fiber is never blocked. Therefore there is always at least one
  53         ready fiber. Therefore the fiber manager never calls <a class="link" href="../scheduling.html#algorithm_suspend_until"><code class="computeroutput">algorithm::suspend_until()</code></a>.
  54       </p>
  55 <p>
  56         Using <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/io_service/post.html" target="_top"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">post</span><span class="special">()</span></code></a>
  57         instead of setting a timer for some nonzero interval would be unfriendly
  58         to other threads. When all I/O is pending and all fibers are blocked, the
  59         io_service and the fiber manager would simply spin the CPU, passing control
  60         back and forth to each other. Using a timer allows tuning the responsiveness
  61         of this thread relative to others.
  62       </p>
  63 </div>
  64 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
  65 <td align="left"></td>
  66 <td align="right"><div class="copyright-footer">Copyright &#169; 2013 Oliver Kowalke<p>
  67         Distributed under the Boost Software License, Version 1.0. (See accompanying
  68         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
  69       </p>
  70 </div></td>
  71 </tr></table>
  72 <hr>
  73 <div class="spirit-nav">
  74 <a accesskey="p" href="event_driven_program.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../integration.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="deeper_dive_into___boost_asio__.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
  75 </div>
  76 </body>
  77 </html>