55 lines
3.4 KiB
HTML
55 lines
3.4 KiB
HTML
|
<?xml version="1.0" encoding="UTF-8"?>
|
||
|
|
<!DOCTYPE html
|
||
|
|
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||
|
|
<html lang="en-us" xml:lang="en-us">
|
||
|
|
<head>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
||
|
|
<meta name="security" content="public" />
|
||
|
|
<meta name="Robots" content="index,follow" />
|
||
|
|
<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
|
||
|
|
<meta name="DC.Type" content="concept" />
|
||
|
|
<meta name="DC.Title" content="Thread models" />
|
||
|
|
<meta name="abstract" content="There are different models of thread usage: user threads and kernel threads." />
|
||
|
|
<meta name="description" content="There are different models of thread usage: user threads and kernel threads." />
|
||
|
|
<meta name="DC.Relation" scheme="URI" content="rzahwas4co.htm" />
|
||
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
|
||
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
|
||
|
|
<meta name="DC.Format" content="XHTML" />
|
||
|
|
<meta name="DC.Identifier" content="rzahwker-kerco" />
|
||
|
|
<meta name="DC.Language" content="en-us" />
|
||
|
|
<!-- All rights reserved. Licensed Materials Property of IBM -->
|
||
|
|
<!-- US Government Users Restricted Rights -->
|
||
|
|
<!-- Use, duplication or disclosure restricted by -->
|
||
|
|
<!-- GSA ADP Schedule Contract with IBM Corp. -->
|
||
|
|
<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
|
||
|
|
<link rel="stylesheet" type="text/css" href="./ic.css" />
|
||
|
|
<title>Thread models</title>
|
||
|
|
</head>
|
||
|
|
<body id="rzahwker-kerco"><a name="rzahwker-kerco"><!-- --></a>
|
||
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
||
|
|
<h1 class="topictitle1">Thread models</h1>
|
||
|
|
<div><p>There are different models of thread usage: user threads and kernel
|
||
|
|
threads.</p>
|
||
|
|
<p>In the user threads model, all program threads share the same process thread.
|
||
|
|
In the user thread model, the thread application programming interfaces (APIs)
|
||
|
|
enforce the scheduling policy and decide when a new thread runs. The scheduling
|
||
|
|
policy allows only one thread to be actively running in the process at a time.
|
||
|
|
The operating system kernel is only aware of a single task in the process.</p>
|
||
|
|
<p>In the kernel threads model, kernel threads are separate tasks that are
|
||
|
|
associated with a process. The kernel thread model uses a preemptive scheduling
|
||
|
|
policy in which the operating system decides which thread is eligible to share
|
||
|
|
the processor. In a kernel thread model, there is a one-to-one mapping between
|
||
|
|
program threads and process threads. <span class="keyword">i5/OS™</span> supports
|
||
|
|
a kernel thread model.</p>
|
||
|
|
<p>Some platforms support a combination of these two thread models commonly
|
||
|
|
referred to as an MxN thread model. Each process has M user threads that share
|
||
|
|
N kernel threads. The user threads are scheduled on top of the kernel threads.
|
||
|
|
The system allocates resources only to the more "expensive" kernel threads.</p>
|
||
|
|
</div>
|
||
|
|
<div>
|
||
|
|
<div class="familylinks">
|
||
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzahwas4co.htm" title="All programs have at least one thread, referred to as the initial thread. In a program with multiple threads, each thread runs its code independently of the other threads in the program.">Threads on i5/OS</a></div>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
</body>
|
||
|
|
</html>
|