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branches/samba-3.3.x/docs/htmldocs/Samba3-Developers-Guide/architecture.html
r368 r411 1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 3. Samba Architecture</title><link rel="stylesheet" href="../samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.7 5.2"><link rel="home" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt02.html" title="Part II. Samba Basics"><link rel="prev" href="pt02.html" title="Part II. Samba Basics"><link rel="next" href="debug.html" title="Chapter 4. The samba DEBUG system"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 3. Samba Architecture</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="pt02.html">Prev</a> </td><th width="60%" align="center">Part II. Samba Basics</th><td width="20%" align="right"> <a accesskey="n" href="debug.html">Next</a></td></tr></table><hr></div><div class="chapter" title="Chapter 3. Samba Architecture"><div class="titlepage"><div><div><h2 class="title"><a name="architecture"></a>Chapter 3. Samba Architecture</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Dan</span> <span class="surname">Shearer</span></h3></div></div><div><p class="pubdate"> November 1997</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="architecture.html#id2562765">Introduction</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2562808">Multithreading and Samba</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2562839">Threading smbd</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2562900">Threading nmbd</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2562945">nbmd Design</a></span></dt></dl></div><div class="sect1" title="Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2562765"></a>Introduction</h2></div></div></div><p>1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 3. Samba Architecture</title><link rel="stylesheet" href="../samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.74.0"><link rel="home" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt02.html" title="Part II. Samba Basics"><link rel="prev" href="pt02.html" title="Part II. Samba Basics"><link rel="next" href="debug.html" title="Chapter 4. The samba DEBUG system"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 3. Samba Architecture</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="pt02.html">Prev</a> </td><th width="60%" align="center">Part II. Samba Basics</th><td width="20%" align="right"> <a accesskey="n" href="debug.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="architecture"></a>Chapter 3. Samba Architecture</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Dan</span> <span class="surname">Shearer</span></h3></div></div><div><p class="pubdate"> November 1997</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="architecture.html#id2556692">Introduction</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2556735">Multithreading and Samba</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2556767">Threading smbd</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2556828">Threading nmbd</a></span></dt><dt><span class="sect1"><a href="architecture.html#id2556873">nbmd Design</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2556692"></a>Introduction</h2></div></div></div><p> 2 2 This document gives a general overview of how Samba works 3 3 internally. The Samba Team has tried to come up with a model which is … … 7 7 </p><p> 8 8 It also tries to answer some of the frequently asked questions such as: 9 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>9 </p><div class="orderedlist"><ol type="1"><li><p> 10 10 Is Samba secure when running on Unix? The xyz platform? 11 11 What about the root priveliges issue? 12 </p></li><li class="listitem"><p>Pros and cons of multithreading in various parts of Samba</p></li><li class="listitem"><p>Why not have a separate process for name resolution, WINS, and browsing?</p></li></ol></div></div><div class="sect1" title="Multithreading and Samba"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2562808"></a>Multithreading and Samba</h2></div></div></div><p>12 </p></li><li><p>Pros and cons of multithreading in various parts of Samba</p></li><li><p>Why not have a separate process for name resolution, WINS, and browsing?</p></li></ol></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2556735"></a>Multithreading and Samba</h2></div></div></div><p> 13 13 People sometimes tout threads as a uniformly good thing. They are very 14 14 nice in their place but are quite inappropriate for smbd. nmbd is … … 27 27 that we use a separate process for each connection is one of Samba's 28 28 biggest advantages. 29 </p></div><div class="sect1" title="Threading smbd"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2562839"></a>Threading smbd</h2></div></div></div><p>29 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2556767"></a>Threading smbd</h2></div></div></div><p> 30 30 A few problems that would arise from a threaded smbd are: 31 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>31 </p><div class="orderedlist"><ol type="1"><li><p> 32 32 It's not only to create threads instead of processes, but you 33 33 must care about all variables if they have to be thread specific 34 34 (currently they would be global). 35 </p></li><li class="listitem"><p>35 </p></li><li><p> 36 36 if one thread dies (eg. a seg fault) then all threads die. We can 37 37 immediately throw robustness out the window. 38 </p></li><li class="listitem"><p>38 </p></li><li><p> 39 39 many of the system calls we make are blocking. Non-blocking 40 40 equivalents of many calls are either not available or are awkward (and … … 42 42 waiting. Imagine if one share is a slow NFS filesystem and the others 43 43 are fast, we will end up slowing all clients to the speed of NFS. 44 </p></li><li class="listitem"><p>44 </p></li><li><p> 45 45 you can't run as a different uid in different threads. This means 46 46 we would have to switch uid/gid on _every_ SMB packet. It would be 47 47 horrendously slow. 48 </p></li><li class="listitem"><p>48 </p></li><li><p> 49 49 the per process file descriptor limit would mean that we could only 50 50 support a limited number of clients. 51 </p></li><li class="listitem"><p>51 </p></li><li><p> 52 52 we couldn't use the system locking calls as the locking context of 53 53 fcntl() is a process, not a thread. 54 </p></li></ol></div></div><div class="sect1" title="Threading nmbd"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2562900"></a>Threading nmbd</h2></div></div></div><p>54 </p></li></ol></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2556828"></a>Threading nmbd</h2></div></div></div><p> 55 55 This would be ideal, but gets sunk by portability requirements. 56 56 </p><p> … … 79 79 complex structures) between the processes. We can't rely on each 80 80 platform having a shared memory system. 81 </p></div><div class="sect1" title="nbmd Design"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2562945"></a>nbmd Design</h2></div></div></div><p>81 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2556873"></a>nbmd Design</h2></div></div></div><p> 82 82 Originally Andrew used recursion to simulate a multi-threaded 83 83 environment, which use the stack enormously and made for really
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