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iocp-links: clean up introduction

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Ryan Dahl 2011-04-03 11:34:07 -07:00
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iocp-links.html
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@ -45,35 +45,26 @@
<p>This document assumes you are familiar with how non-blocking socket I/O
is done in Unix.
<p>Windows presents asynchronous and non-blocking I/O differently than in Unix.
The syscall
<a href="http://msdn.microsoft.com/en-us/library/ms740141(v=VS.85).aspx"><code>select()</code>
is available in Windows</a>.
<code>select</code> processing is O(n) in the number of file descriptors
unlike the modern constant-time multiplexers like epoll which makes it
<p>The syscall
<a href="http://msdn.microsoft.com/en-us/library/ms740141(v=VS.85).aspx"><code>select</code>
is available in Windows</a>
but <code>select</code> processing is O(n) in the number of file descriptors
unlike the modern constant-time multiplexers like epoll which makes select
unacceptable for high-concurrency servers.
This document will describe how high-concurrency programs are
designed in Windows.
<p>
Windows has another way of polling called
Instead of <a href="http://en.wikipedia.org/wiki/Epoll">epoll</a>
or
<a href="http://en.wikipedia.org/wiki/Kqueue">kqueue</a>,
Windows has its own I/O multiplexer called
<a href="http://msdn.microsoft.com/en-us/library/aa365198(VS.85).aspx">I/O completion ports</a>
(IOCPs). IOCPs are the objects used to poll
<a href="http://msdn.microsoft.com/en-us/library/ms686358(v=vs.85).aspx">overlapped I/O</a>
for completion. IOCP polling is constant time (REF?).
They are similar to the Unix I/O multiplexers
<ul>
<li> <a
href="http://en.wikipedia.org/wiki/Kqueue">kqueue</a> on Macintosh and
BSDs,
<li> <a href="http://en.wikipedia.org/wiki/Epoll">epoll</a>
on Linux,
<li> <a
href="http://developers.sun.com/solaris/articles/event_completion.html">event
completion ports</a> on Solaris,
<li> <a href="">poll</a> on modern Unixes, and
<li> <a
href="http://www.kernel.org/doc/man-pages/online/pages/man2/select.2.html"><code>select()</code></a>,
which is available everywhere.
</ul>
<p>
The fundamental variation is that in a Unix you generally ask the kernel to
wait for state change in a file descriptor's readability or writablity. With
overlapped I/O and IOCPs the programmers waits for asynchronous function