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From rbo...@apache.org
Subject svn commit: r1330282 [2/4] - in /httpd/httpd/trunk/docs/manual/misc: perf-scaling.html.en perf-scaling.xml
Date Wed, 25 Apr 2012 13:32:56 GMT

Modified: httpd/httpd/trunk/docs/manual/misc/perf-scaling.html.en
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/docs/manual/misc/perf-scaling.html.en?rev=1330282&r1=1330281&r2=1330282&view=diff
==============================================================================
--- httpd/httpd/trunk/docs/manual/misc/perf-scaling.html.en (original)
+++ httpd/httpd/trunk/docs/manual/misc/perf-scaling.html.en Wed Apr 25 13:32:55 2012
@@ -1,1678 +1,1663 @@
-<?xml version="1.0" encoding="ISO-8859-1"?>
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
-<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
-        XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-              This file is generated from xml source: DO NOT EDIT
-        XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-      -->
-<title>Performance Scaling
-     - Apache HTTP Server</title>
-<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
-<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
-<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
-<script src="../style/scripts/prettify.js" type="text/javascript">
-</script>
-
-<link href="../images/favicon.ico" rel="shortcut icon" /></head>
-<body id="manual-page"><div id="page-header">
-<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
-<p class="apache">Apache HTTP Server Version 2.5</p>
-<img alt="" src="../images/feather.gif" /></div>
-<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
-<div id="path">
-<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.5</a></div><div id="page-content"><div id="preamble"><h1>Performance Scaling
-    </h1>
-<div class="toplang">
-<p><span>Available Languages: </span><a href="../en/misc/perf-scaling.html" title="English">&nbsp;en&nbsp;</a></p>
-</div>
-
-        
-        <p>The Performance Tuning page in the Apache 1.3 documentation says: 
-        </p>
-        <ul>
-            <li>&#8220;Apache is a general webserver, which is designed to be
-                correct first, and fast
-                second. Even so, its performance is quite satisfactory. Most
-                sites have less than 10Mbits of outgoing bandwidth, which
-                Apache can fill using only a low end Pentium-based
-                webserver.&#8221; 
-            </li>
-        </ul>
-        <p>However, this sentence was written a few years ago, and in the
-            meantime several things have happened. On one hand, web server
-            hardware has become much faster. On the other hand, many sites now
-            are allowed much more than ten megabits per second of outgoing
-            bandwidth. In addition, web applications have become more complex.
-            The classic brochureware site is alive and well, but the web has
-            grown up substantially as a computing application platform and
-            webmasters may find themselves running dynamic content in Perl, PHP
-            or Java, all of which take a toll on performance. 
-        </p>
-        <p>Therefore, in spite of strides forward in machine speed and
-            bandwidth allowances, web server performance and web application
-            performance remain areas of concern. In this documentation several
-            aspects of web server performance will be discussed. 
-        </p>
-        
-    </div>
-<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#What Will and Will Not Be Discussed">What Will and Will Not Be Discussed
-        </a></li>
-<li><img alt="" src="../images/down.gif" /> <a href="#Monitoring Your Server">Monitoring Your Server
-        </a></li>
-<li><img alt="" src="../images/down.gif" /> <a href="#Configuring for Performance">Configuring for Performance
-        </a></li>
-<li><img alt="" src="../images/down.gif" /> <a href="#Caching Content">Caching Content
-        </a></li>
-<li><img alt="" src="../images/down.gif" /> <a href="#Further Considerations">Further Considerations
-        </a></li>
-</ul></div>
-<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
-<div class="section">
-<h2><a name="What Will and Will Not Be Discussed" id="What Will and Will Not Be Discussed">What Will and Will Not Be Discussed
-        </a></h2>
-        
-        <p>The session will focus on easily accessible configuration and tuning
-            options for Apache httpd 2.2 and 2.3 as well as monitoring tools.
-            Monitoring tools will allow you to observe your web server to
-            gather information about its performance, or lack thereof.
-            We'll assume that you don't have an unlimited budget for
-            server hardware, so the existing infrastructure will have to do the
-            job. You have no desire to compile your own Apache, or to recompile
-            the operating system kernel. We do assume, though, that you have
-            some familiarity with the Apache httpd configuration file. 
-        </p>
-        
-    </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
-<div class="section">
-<h2><a name="Monitoring Your Server" id="Monitoring Your Server">Monitoring Your Server
-        </a></h2>
-        
-        <p>The first task when sizing or performance-tuning your server is to
-            find out how your system is currently performing. By monitoring
-            your server under real-world load, or artificially generated load,
-            you can extrapolate its behavior under stress, such as when your
-            site is mentioned on Slashdot. 
-        </p>
-        
-        
-        <h3><a name="Monitoring Tools" id="Monitoring Tools">Monitoring Tools
-            </a></h3>
-            
-            
-            
-            <h4><a name="top" id="top">top
-                </a></h4>
-                
-                <p>The top tool ships with Linux and FreeBSD. Solaris offers
-                    `prstat'. It collects a number of statistics for the
-                    system and for each running process, then displays them
-                    interactively on your terminal. The data displayed is
-                    refreshed every second and varies by platform, but
-                    typically includes system load average, number of processes
-                    and their current states, the percent CPU(s) time spent
-                    executing user and system code, and the state of the
-                    virtual memory system. The data displayed for each process
-                    is typically configurable and includes its process name and
-                    ID, priority and nice values, memory footprint, and
-                    percentage CPU usage. The following example shows multiple
-                    httpd processes (with MPM worker and event) running on an
-                    Linux (Xen) system: 
-                </p>
-                
-                <div class="example"><p><code>
-                    top - 23:10:58 up 71 days,  6:14,  4 users,  load average:
-                    0.25, 0.53, 0.47<br />
-                    Tasks: 163 total,   1 running, 162 sleeping,   0 stopped,  
-                    0 zombie<br />
-                    Cpu(s): 11.6%us,  0.7%sy,  0.0%ni, 87.3%id,  0.4%wa, 
-                    0.0%hi,  0.0%si,  0.0%st<br />
-                    Mem:   2621656k total,  2178684k used,   442972k free,  
-                    100500k buffers<br />
-                    Swap:  4194296k total,   860584k used,  3333712k free, 
-                    1157552k cached<br />
-                    <br />
-                    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+ 
-                    COMMAND<br />
-                    16687 example_  20   0 1200m 547m 179m S   45 21.4  
-                    1:09.59 httpd-worker<br />
-                    15195 www       20   0  441m  33m 2468 S    0  1.3  
-                    0:41.41 httpd-worker<br />
-                    1 root      20   0 10312  328  308 S    0  0.0   0:33.17
-                    init<br />
-                    2 root      15  -5     0    0    0 S    0  0.0   0:00.00
-                    kthreadd<br />
-                    3 root      RT  -5     0    0    0 S    0  0.0   0:00.14
-                    migration/0<br />
-                    4 root      15  -5     0    0    0 S    0  0.0   0:04.58
-                    ksoftirqd/0<br />
-                    5 root      RT  -5     0    0    0 S    0  0.0   4:45.89
-                    watchdog/0<br />
-                    6 root      15  -5     0    0    0 S    0  0.0   1:42.52
-                    events/0<br />
-                    7 root      15  -5     0    0    0 S    0  0.0   0:00.00
-                    khelper<br />
-                    19 root      15  -5     0    0    0 S    0  0.0   0:00.00
-                    xenwatch<br />
-                    20 root      15  -5     0    0    0 S    0  0.0   0:00.00
-                    xenbus<br />
-                    28 root      RT  -5     0    0    0 S    0  0.0   0:00.14
-                    migration/1<br />
-                    29 root      15  -5     0    0    0 S    0  0.0   0:00.20
-                    ksoftirqd/1<br />
-                    30 root      RT  -5     0    0    0 S    0  0.0   0:05.96
-                    watchdog/1<br />
-                    31 root      15  -5     0    0    0 S    0  0.0   1:18.35
-                    events/1<br />
-                    32 root      RT  -5     0    0    0 S    0  0.0   0:00.08
-                    migration/2<br />
-                    33 root      15  -5     0    0    0 S    0  0.0   0:00.18
-                    ksoftirqd/2<br />
-                    34 root      RT  -5     0    0    0 S    0  0.0   0:06.00
-                    watchdog/2<br />
-                    35 root      15  -5     0    0    0 S    0  0.0   1:08.39
-                    events/2<br />
-                    36 root      RT  -5     0    0    0 S    0  0.0   0:00.10
-                    migration/3<br />
-                    37 root      15  -5     0    0    0 S    0  0.0   0:00.16
-                    ksoftirqd/3<br />
-                    38 root      RT  -5     0    0    0 S    0  0.0   0:06.08
-                    watchdog/3<br />
-                    39 root      15  -5     0    0    0 S    0  0.0   1:22.81
-                    events/3<br />
-                    68 root      15  -5     0    0    0 S    0  0.0   0:06.28
-                    kblockd/0<br />
-                    69 root      15  -5     0    0    0 S    0  0.0   0:00.04
-                    kblockd/1<br />
-                    70 root      15  -5     0    0    0 S    0  0.0   0:00.04
-                    kblockd/2
-                </code></p></div>
-                
-                <p>Top is a wonderful tool even though it&#8217;s slightly resource
-                    intensive (when running, its own process is usually in the
-                    top ten CPU gluttons). It is indispensable in determining
-                    the size of a running process, which comes in handy when
-                    determining how many server processes you can run on your
-                    machine. How to do this is described in '<a href="/httpd/PerformanceScalingUp#S">
-                        sizing MaxClients
-                    </a>
-                    '. Top is, however, an interactive tool and running it
-                    continuously has few if any advantages. 
-                </p>
-            
-            <h4><a name="free" id="free">free
-                </a></h4>
-                
-                <p>This command is only available on Linux. It shows how much
-                    memory and swap space is in use. Linux allocates unused
-                    memory as file system cache. The free command shows usage
-                    both with and without this cache. The free command can be
-                    used to find out how much memory the operating system is
-                    using, as described in the paragraph '<a href="/httpd/PerformanceScalingUp#S">
-                        Sizing MaxClients
-                    </a>
-                    '. The output of free looks like this: 
-                </p>
-                
-                <div class="example"><p><code>
-                    sctemme@brutus:~$ free<br />
-                    total       used     free   shared    buffers    cached<br />
-                    Mem:        4026028    3901892   124136         0    253144
-                       841044<br />
-                    -/+ buffers/cache:     2807704  1218324<br />
-                    Swap:       3903784      12540  3891244
-                </code></p></div>
-            
-            
-            <h4><a name="vmstat" id="vmstat">vmstat
-                </a></h4>
-                
-                <p>This command is available on many unix platforms. It
-                    displays a large number of operating system metrics. Run
-                    without argument, it displays a status line for that
-                    moment. When a numeric argument is added, the status is
-                    redisplayed at designated intervals. For example, <code>
-                        vmstat 5
-                    </code>
-                    causes the information to reappear every five seconds.
-                    Vmstat displays the amount of virtual memory in use, how
-                    much memory is swapped in and out each second, the number
-                    of processes currently running and sleeping, the number of
-                    interrupts and context switches per second and the usage
-                    percentages of the CPU. 
-                </p>
-                <p>
-                    The following is <code>vmstat
-                    </code>
-                    output of an idle server: 
-                </p>
-                
-                
-                <div class="example"><p><code>
-                    [sctemme@GayDeceiver sctemme]$ vmstat 5 3<br />
-                    procs                      memory     swap         io   
-                    system        cpu<br />
-                    r b w     swpd   free   buff cache si so       bi    bo in 
-                       cs us  sy i<br />
-                    0 0 0        0 186252   6688 37516    0    0   12     5 47 
-                      311  0   1 9<br />
-                    0 0 0        0 186244   6696 37516    0    0    0    16 41 
-                      314  0   0 10<br />
-                    0 0 0        0 186236   6704 37516    0    0    0     9 44 
-                      314  0   0 100
-                </code></p></div>
-                
-                <p>And this is output of a server that is under a load of one
-                    hundred simultaneous connections fetching static content: 
-                </p>
-                
-                <div class="example"><p><code>
-                    sctemme@GayDeceiver sctemme]$ vmstat 5 3<br />
-                    procs                      memory     swap    io     
-                    system       cpu<br />
-                    r b w     swpd   free   buff cache si so     bi bo   in    
-                    cs us sy  id<br />
-                    1 0 1        0 162580   6848 40056    0    0 11  5 150    
-                    324  1  1  98<br />
-                    6 0 1        0 163280   6856 40248    0    0  0 66 6384
-                    1117   42 25  32<br />
-                    11 0 0        0 162780   6864 40436    0    0  0 61 6309
-                    1165   33 28  40
-                </code></p></div>
-                
-                <p>The first line gives averages since the last reboot. The
-                    subsequent lines give information for five second
-                    intervals. The second argument tells vmstat to generate
-                    three reports and then exit. 
-                </p>
-                
-                
-            
-            <h4><a name="SE Toolkit" id="SE Toolkit">SE Toolkit
-                </a></h4>
-                
-                <p>The SE Toolkit is a system monitoring toolkit for Solaris.
-                    Its programming language is based on the C preprocessor and
-                    comes with a number of sample scripts. It can use both the
-                    command line and the GUI to display information. It can
-                    also be programmed to apply rules to the system data. The
-                    example script shown in Figure 2, Zoom.se, shows green,
-                    orange or red indicators when utilization of various parts
-                    of the system rises above certain thresholds. Another
-                    included script, Virtual Adrian, applies performance tuning
-                    metrics according to. 
-                </p>
-                <p>The SE Toolkit has drifted around for a while and has had
-                    several owners since its inception. It seems that it has
-                    now found a final home at Sunfreeware.com, where it can be
-                    downloaded at no charge. There is a single package for
-                    Solaris 8, 9 and 10 on SPARC and x86, and includes source
-                    code. SE Toolkit author Richard Pettit has started a new
-                    company, Captive Metrics4 that plans to bring to market a
-                    multiplatform monitoring tool built on the same principles
-                    as SE Toolkit, written in Java. 
-                </p>
-                
-                
-            
-            <h4><a name="DTrace" id="DTrace">DTrace
-                </a></h4>
-                
-                <p>Given that DTrace is available for Solaris, FreeBSD and OS
-                    X, it might be worth exploring it. There's also
-                    mod_dtrace available for httpd. 
-                </p>
-                
-                
-            
-            <h4><a name="mod_status" id="mod_status">mod_status
-                </a></h4>
-                
-                <p>The mod_status module gives an overview of the server
-                    performance at a given moment. It generates an HTML page
-                    with, among others, the number of Apache processes running
-                    and how many bytes each has served, and the CPU load caused
-                    by httpd and the rest of the system. The Apache Software
-                    Foundation uses mod_status on its own <a href="http://apache.org/server-status">
-                        web site
-                    </a>
-                    .If you put the <code>ExtendedStatus On
-                    </code>
-                    directive in your <code>httpd.conf
-                    </code>
-                    ,the <code>mod_status
-                    </code>
-                    page will give you more information at the cost of a little
-                    extra work per request. 
-                </p>
-                
-                
-            
-        
-        <h3><a name="Web Server Log Files" id="Web Server Log Files">Web Server Log Files
-            </a></h3>
-            
-            <p>Monitoring and analyzing the log files httpd writes is one of
-                the most effective ways to keep track of your server health and
-                performance. Monitoring the error log allows you to detect
-                error conditions, discover attacks and find performance issues.
-                Analyzing the access logs tells you how busy your server is,
-                which resources are the most popular and where your users come
-                from. Historical log file data can give you invaluable insight
-                into trends in access to your server, which allows you to
-                predict when your performance needs will overtake your server
-                capacity. 
-            </p>
-            
-            
-            <h4><a name="Error Log" id="Error Log">Error Log
-                </a></h4>
-                
-                <p>The error log will contain messages if the server has
-                    reached the maximum number of active processes or the
-                    maximum number of concurrently open files. The error log
-                    also reflects when processes are being spawned at a
-                    higher-than-usual rate in response to a sudden increase in
-                    load. When the server starts, the stderr file descriptor is
-                    redirected to the error logfile, so any error encountered
-                    by httpd after it opens its logfiles will appear in this
-                    log. This makes it good practice to review the error log
-                    frequently. 
-                </p>
-                <p>Before Apache httpd opens its logfiles, any errors will be
-                    written to the stderr stream. If you start httpd manually,
-                    this error information will appear on your terminal and you
-                    can use it directly to troubleshoot your server. If your
-                    httpd is started by a startup script, the destination of
-                    early error messages depends on their design. The <code>
-                        /var/log/messages
-                    </code>
-                    file is usually a good bet. On Windows, early error
-                    messages are written to the Applications Event Log, which
-                    can be viewed through the Event Viewer in Administrative
-                    Tools. 
-                </p>
-                <p>
-                    The Error Log is configured through the <code>ErrorLog
-                    </code>
-                    and <code>LogLevel
-                    </code>
-                    configuration directives. The error log of httpd&#8217;s main
-                    server configuration receives the log messages that pertain
-                    to the entire server: startup, shutdown, crashes, excessive
-                    process spawns, etc. The <code>ErrorLog
-                    </code>
-                    directive can also be used in virtual host containers. The
-                    error log of a virtual host receives only log messages
-                    specific to that virtual host, such as authentication
-                    failures and 'File not Found' errors. 
-                </p>
-                <p>On a server that is visible to the Internet, expect to see a
-                    lot of exploit attempt and worm attacks in the error log. A
-                    lot of these will be targeted at other server platforms
-                    instead of Apache, but the current state of affairs is that
-                    attack scripts just throw everything they have at any open
-                    port, regardless of which server is actually running or
-                    what applications might be installed. You could block these
-                    attempts using a firewall or <a href="http://www.modsecurity.org/">
-                        mod_security
-                    </a>
-                    ,but this falls outside the scope of this discussion. 
-                </p>
-                <p>
-                    The <code>LogLevel
-                    </code>
-                    directive determines the level of detail included in the
-                    logs. There are eight log levels as described here: 
-                </p>
-                <table>
-                    <tr>
-                        <td>
-                            <p>
-                                 <strong>Level
-                                </strong>
-                            </p>
-                        </td>
-                        <td>
-                            <p>
-                                 <strong>Description
-                                </strong>
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> emerg 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Emergencies - system is unusable. 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> alert 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Action must be taken immediately. 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> crit 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Critical Conditions. 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> error 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Error conditions. 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> warn 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Warning conditions. 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> notice 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Normal but significant condition. 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> info 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Informational. 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> debug 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Debug-level messages 
-                            </p>
-                        </td>
-                    </tr>
-                </table>
-                <p>The default log level is warn. A production server should
-                    not be run on debug, but increasing the level of detail in
-                    the error log can be useful during troubleshooting.
-                    Starting with 2.3.8 <code>LogLevel
-                    </code>
-                    can be specified on a per module basis: 
-                </p>
-                
-                <div class="example"><p><code>
-                    LogLevel debug mod_ssl:warn
-                </code></p></div>
-                
-                <p>
-                    This puts all of the server in debug mode, except for <code>
-                        mod_ssl
-                    </code>
-                    ,which tends to be very noisy. 
-                </p>
-                
-                
-            
-            <h4><a name="Access Log" id="Access Log">Access Log
-                </a></h4>
-                
-                <p>Apache httpd keeps track of every request it services in its
-                    access log file. In addition to the time and nature of a
-                    request, httpd can log the client IP address, date and time
-                    of the request, the result and a host of other information.
-                    The various logging format features are documented in the <a href="http://httpd.apache.org/docs/current/mod/core.html#loglevel">
-                        manual
-                    </a>
-                    .This file exists by default for the main server and can be
-                    configured per virtual host by using the <code>TransferLog
-                    </code>
-                    or <code>CustomLog
-                    </code>
-                    configuration directive. 
-                </p>
-                <p>The access logs can be analyzed with any of several free and
-                    commercially available programs. Popular free analysis
-                    packages include Analog and Webalizer. Log analysis should
-                    be done offline so the web server machine is not burdened
-                    by processing the log files. Most log analysis packages
-                    understand the Common Log Format. The fields in the log
-                    lines are explained in in the following: 
-                </p>
-                
-                
-                <div class="example"><p><code>
-                    195.54.228.42 - - [24/Mar/2007:23:05:11 -0400] "GET
-                    /sander/feed/ HTTP/1.1" 200 9747<br />
-                    64.34.165.214 - - [24/Mar/2007:23:10:11 -0400] "GET
-                    /sander/feed/atom HTTP/1.1" 200 9068<br />
-                    60.28.164.72 - - [24/Mar/2007:23:11:41 -0400] "GET /
-                    HTTP/1.0" 200 618<br />
-                    85.140.155.56 - - [24/Mar/2007:23:14:12 -0400] "GET
-                    /sander/2006/09/27/44/ HTTP/1.1" 200 14172<br />
-                    85.140.155.56 - - [24/Mar/2007:23:14:15 -0400] "GET
-                    /sander/2006/09/21/gore-tax-pollution/ HTTP/1.1" 200 15147<br />
-                    74.6.72.187 - - [24/Mar/2007:23:18:11 -0400] "GET
-                    /sander/2006/09/27/44/ HTTP/1.0" 200 14172<br />
-                    74.6.72.229 - - [24/Mar/2007:23:24:22 -0400] "GET
-                    /sander/2006/11/21/os-java/ HTTP/1.0" 200 13457
-                </code></p></div>
-                
-                <table>
-                    <tr>
-                        <td>
-                            <p>
-                                 <strong>Field
-                                </strong>
-                            </p>
-                        </td>
-                        <td>
-                            <p>
-                                 <strong>Content
-                                </strong>
-                            </p>
-                        </td>
-                        <td>
-                            <p>
-                                 <strong>Explanation
-                                </strong>
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> Client IP 
-                            </p>
-                        </td>
-                        <td>
-                            <p> 195.54.228.42 
-                            </p>
-                        </td>
-                        <td>
-                            <p> IP address where the request originated 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> RFC 1413 ident 
-                            </p>
-                        </td>
-                        <td>
-                            <p> -  
-                            </p>
-                        </td>
-                        <td>
-                            <p> Remote user identity as reported by their
-                                identd 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> username 
-                            </p>
-                        </td>
-                        <td>
-                            <p> -   
-                            </p>
-                        </td>
-                        <td>
-                            <p> Remote username as authenticated by Apache 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> timestamp 
-                            </p>
-                        </td>
-                        <td>
-                            <p> [24/Mar/2007:23:05:11 -0400] 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Date and time of request 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> Request 
-                            </p>
-                        </td>
-                        <td>
-                            <p> "GET /sander/feed/ HTTP/1.1"  
-                            </p>
-                        </td>
-                        <td>
-                            <p> Request line 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> Status Code 
-                            </p>
-                        </td>
-                        <td>
-                            <p> 200  
-                            </p>
-                        </td>
-                        <td>
-                            <p> Response code 
-                            </p>
-                        </td>
-                    </tr>
-                    <tr>
-                        <td>
-                            <p> Content Bytes 
-                            </p>
-                        </td>
-                        <td>
-                            <p> 9747 
-                            </p>
-                        </td>
-                        <td>
-                            <p> Bytes transferred w/o headers 
-                            </p>
-                        </td>
-                    </tr>
-                </table>
-                
-            
-            <h4><a name="Rotating Log Files" id="Rotating Log Files">Rotating Log Files
-                </a></h4>
-                
-                <p>There are several reasons to rotate logfiles. Even though
-                    almost no operating systems out there have a hard file size
-                    limit of two Gigabytes anymore, log files simply become too
-                    large to handle over time. Additionally, any periodic log
-                    file analysis should not be performed on files to which the
-                    server is actively writing. Periodic logfile rotation helps
-                    keep the analysis job manageable, and allows you to keep a
-                    closer eye on usage trends. 
-                </p>
-                <p>On unix systems, you can simply rotate logfiles by giving
-                    the old file a new name using mv. The server will keep
-                    writing to the open file even though it has a new name.
-                    When you send a graceful restart signal to the server, it
-                    will open a new logfile with the configured name. For
-                    example, you could run a script from cron like this: 
-                </p>
-                
-                
-                <div class="example"><p><code>
-                    APACHE=/usr/local/apache2<br />
-                    HTTPD=$APACHE/bin/httpd<br />
-                    mv $APACHE/logs/access_log
-                    $APACHE/logarchive/access_log-&#8216;date +%F&#8216;<br />
-                    $HTTPD -k graceful
-                </code></p></div>
-                
-                <p>This approach also works on Windows, just not as smoothly.
-                    While the httpd process on your Windows server will keep
-                    writing to the log file after it has been renamed, the
-                    Windows Service that runs Apache can not do a graceful
-                    restart. Restarting a Service on Windows means stopping it
-                    and then starting it again. The advantage of a graceful
-                    restart is that the httpd child processes get to complete
-                    responding to their current requests before they exit.
-                    Meanwhile, the httpd server becomes immediately available
-                    again to serve new requests. The stop-start that the
-                    Windows Service has to perform will interrupt any requests
-                    currently in progress, and the server is unavailable until
-                    it is started again. Plan for this when you decide the
-                    timing of your restarts. 
-                </p>
-                <p>
-                    A second approach is to use piped logs. From the <code>
-                        CustomLog
-                    </code>
-                    ,<code>TransferLog
-                    </code>
-                    or <code>ErrorLog
-                    </code>
-                    directives you can send the log data into any program using
-                    a pipe character (<code>|
-                    </code>
-                    ). For instance: 
-                </p>
-                
-                <div class="example"><p><code>CustomLog "|/usr/local/apache2/bin/rotatelogs
-                    /var/log/access_log 86400" common
-                </code></p></div>
-                
-                <p>The program on the other end of the pipe will receive the
-                    Apache log data on its stdin stream, and can do with this
-                    data whatever it wants. The rotatelogs program that comes
-                    with Apache seamlessly turns over the log file based on
-                    time elapsed or the amount of data written, and leaves the
-                    old log files with a timestamp suffix to its name. This
-                    method for rotating logfiles works well on unix platforms,
-                    but is currently broken on Windows. 
-                </p>
-                
-                
-            
-            <h4><a name="Logging and Performance" id="Logging and Performance">Logging and Performance
-                </a></h4>
-                
-                <p>Writing entries to the Apache log files obviously takes some
-                    effort, but the information gathered from the logs is so
-                    valuable that under normal circumstances logging should not
-                    be turned off. For optimal performance, you should put your
-                    disk-based site content on a different physical disk than
-                    the server log files: the access patterns are very
-                    different. Retrieving content from disk is a read operation
-                    in a fairly random pattern, and log files are written to
-                    disk sequentially. 
-                </p>
-                <p>
-                    Do not run a production server with your error <code>
-                        LogLevel
-                    </code>
-                    set to debug. This log level causes a vast amount of
-                    information to be written to the error log, including, in
-                    the case of SSL access, complete dumps of BIO read and
-                    write operations. The performance implications are
-                    significant: use the default warn level instead. 
-                </p>
-                <p>If your server has more than one virtual host, you may give
-                    each virtual host a separate access logfile. This makes it
-                    easier to analyze the logfile later. However, if your
-                    server has many virtual hosts, all the open logfiles put a
-                    resource burden on your system, and it may be preferable to
-                    log to a single file. Use the <code>%v
-                    </code>
-                    format character at the start of your <a href="/httpd/LogFormat" class="nonexistent">
-                        LogFormat
-                    </a>
-                    and starting 2.3.8 of your <code>ErrorLogFormat
-                    </code>
-                    to make httpd print the hostname of the virtual host that
-                    received the request or the error at the beginning of each
-                    log line. A simple Perl script can split out the log file
-                    after it rotates: one is included with the Apache source
-                    under <code>support/split-logfile
-                    </code>
-                    .
-                </p>
-                <p>
-                    You can use the <code>BufferedLogs
-                    </code>
-                    directive to have Apache collect several log lines in
-                    memory before writing them to disk. This might yield better
-                    performance, but could affect the order in which the
-                    server's log is written. 
-                </p>
-                
-                
-            
-        
-        <h3><a name="Generating A Test Load" id="Generating A Test Load">Generating A Test Load
-            </a></h3>
-            
-            <p>It is useful to generate a test load to monitor system
-                performance under realistic operating circumstances. Besides
-                commercial packages such as <a href="/httpd/LoadRunner" class="nonexistent">
-                    LoadRunner
-                </a>
-                ,there are a number of freely available tools to generate a
-                test load against your web server. 
-            </p>
-            <ul>
-                <li>Apache ships with a test program called ab, short for
-                    Apache Bench. It can generate a web server load by
-                    repeatedly asking for the same file in rapid succession.
-                    You can specify a number of concurrent connections and have
-                    the program run for either a given amount of time or a
-                    specified number of requests. 
-                </li>
-                <li>Another freely available load generator is http load11 .
-                    This program works with a URL file and can be compiled with
-                    SSL support. 
-                </li>
-                <li>The Apache Software Foundation offers a tool named flood12
-                    . Flood is a fairly sophisticated program that is
-                    configured through an XML file. 
-                </li>
-                <li>Finally, JMeter13 , a Jakarta subproject, is an all-Java
-                    load-testing tool. While early versions of this application
-                    were slow and difficult to use, the current version 2.1.1
-                    seems to be versatile and useful. 
-                </li>
-                <li>
-                    <p>ASF external projects, that have proven to be quite
-                        good: grinder, httperf, tsung, <a href="/httpd/FunkLoad" class="nonexistent">
-                            FunkLoad
-                        </a>
-                    </p>
-                </li>
-            </ul>
-            <p>When you load-test your web server, please keep in mind that if
-                that server is in production, the test load may negatively
-                affect the server&#8217;s response. Also, any data traffic you
-                generate may be charged against your monthly traffic allowance.
-            </p>
-            
-            
-        
-    </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
-<div class="section">
-<h2><a name="Configuring for Performance" id="Configuring for Performance">Configuring for Performance
-        </a></h2>
-        
-        
-        
-        <h3><a name="Apache Configuration" id="Apache Configuration">Apache Configuration
-            </a></h3>
-            
-            <p>The Apache 2.2 httpd is by default a pre-forking web server.
-                When the server starts, the parent process spawns a number of
-                child processes that do the actual work of servicing requests.
-                But Apache httpd 2.0 introduced the concept of the
-                Multi-Processing Module (MPM). Developers can write MPMs to
-                suit the process- or threadingarchitecture of their specific
-                operating system. Apache 2 comes with special MPMs for Windows,
-                OS/2, Netware and BeOS. On unix-like platforms, the two most
-                popular MPMs are Prefork and Worker. The Prefork MPM offers the
-                same pre-forking process model that Apache 1.3 uses. The Worker
-                MPM runs a smaller number of child processes, and spawns
-                multiple request handling threads within each child process. In
-                2.3+ MPMs are no longer hard-wired. They too can be exchanged
-                via <a href="/httpd/LoadModule" class="nonexistent">LoadModule
-                </a>
-                .The default MPM in 2.3 is the event MPM. 
-            </p>
-            <p>The maximum number of workers, be they pre-forked child
-                processes or threads within a process, is an indication of how
-                many requests your server can manage concurrently. It is merely
-                a rough estimate because the kernel can queue connection
-                attempts for your web server. When your site becomes busy and
-                the maximum number of workers is running, the machine
-                doesn't hit a hard limit beyond which clients will be
-                denied access. However, once requests start backing up, system
-                performance is likely to degrade. 
-            </p>
-            
-            
-            <h4><a name="MaxClients" id="MaxClients">MaxClients
-                </a></h4>
-                
-                <p>
-                    The <code>MaxClients
-                    </code>
-                    directive in your Apache httpd configuration file specifies
-                    the maximum number of workers your server can create. It
-                    has two related directives, <code>MinSpareServers
-                    </code>
-                    and <code>MaxSpareServers
-                    </code>
-                    ,which specify the number of workers Apache keeps waiting
-                    in the wings ready to serve requests. The absolute maximum
-                    number of processes is configurable through the <code>
-                        ServerLimit
-                    </code>
-                    directive. 
-                </p>
-                
-                
-            
-            <h4><a name="Spinning Threads" id="Spinning Threads">Spinning Threads
-                </a></h4>
-                
-                <p>For the prefork MPM of the above directives are all there is
-                    to determining the process limit. However, if you are
-                    running a threaded MPM the situation is a little more
-                    complicated. Threaded MPMs support the <code>
-                        ThreadsPerChild
-                    </code>
-                    directive1 . Apache requires that <code>MaxClients
-                    </code>
-                    is evenly divisible by <code>ThreadsPerChild
-                    </code>
-                    .If you set either directive to a number that doesn&#8217;t
-                    meet this requirement, Apache will send a message of
-                    complaint to the error log and adjust the <code>
-                        ThreadsPerChild
-                    </code>
-                    value downwards until it is an even factor of <code>
-                        MaxClients
-                    </code>
-                    .
-                </p>
-                
-                
-            
-            <h4><a name="Sizing MaxClients" id="Sizing MaxClients">Sizing MaxClients
-                </a></h4>
-                
-                <p>Optimally, the maximum number of processes should be set so
-                    that all the memory on your system is used, but no more. If
-                    your system gets so overloaded that it needs to heavily
-                    swap core memory out to disk, performance will degrade
-                    quickly. The formula for determining <code>MaxClients
-                    </code>
-                    is fairly simple: 
-                </p>
-                
-                <div class="example"><p><code>
-                    total RAM &#8722; RAM for OS &#8722; RAM for external programs<br />
-                    MaxClients =
-                    -------------------------------------------------------<br />
-                    RAM per httpd process
-                </code></p></div>
-                
-                <p>The various amounts of memory allocated for the OS, external
-                    programs and the httpd processes is best determined by
-                    observation: use the top and free commands described above
-                    to determine the memory footprint of the OS without the web
-                    server running. You can also determine the footprint of a
-                    typical web server process from top: most top
-                    implementations have a Resident Size (RSS) column and a
-                    Shared Memory column. 
-                </p>
-                <p>The difference between these two is the amount of memory
-                    per-process. The shared segment really exists only once and
-                    is used for the code and libraries loaded and the dynamic
-                    inter-process tally, or 'scoreboard,' that Apache
-                    keeps. How much memory each process takes for itself
-                    depends heavily on the number and kind of modules you use.
-                    The best approach to use in determining this need is to
-                    generate a typical test load against your web site and see
-                    how large the httpd processes become. 
-                </p>
-                <p>The RAM for external programs parameter is intended mostly
-                    for CGI programs and scripts that run outside the web
-                    server process. However, if you have a Java virtual machine
-                    running Tomcat on the same box it will need a significant
-                    amount of memory as well. The above assessment should give
-                    you an idea how far you can push <code>MaxClients
-                    </code>
-                    ,but it is not an exact science. When in doubt, be
-                    conservative and use a low <code>MaxClients
-                    </code>
-                    value. The Linux kernel will put extra memory to good use
-                    for caching disk access. On Solaris you need enough
-                    available real RAM memory to create any process. If no real
-                    memory is available, httpd will start writing &#8216;No space
-                    left on device&#8217; messages to the error log and be unable
-                    to fork additional child processes, so a higher <code>
-                        MaxClients
-                    </code>
-                    value may actually be a disadvantage. 
-                </p>
-                
-                
-            
-            <h4><a name="Selecting your MPM" id="Selecting your MPM">Selecting your MPM
-                </a></h4>
-                
-                <p>The prime reason for selecting a threaded MPM is that
-                    threads consume fewer system resources than processes, and
-                    it takes less effort for the system to switch between
-                    threads. This is more true for some operating systems than
-                    for others. On systems like Solaris and AIX, manipulating
-                    processes is relatively expensive in terms of system
-                    resources. On these systems, running a threaded MPM makes
-                    sense. On Linux, the threading implementation actually uses
-                    one process for each thread. Linux processes are relatively
-                    lightweight, but it means that a threaded MPM offers less
-                    of a performance advantage than in other environments. 
-                </p>
-                <p>Running a threaded MPM can cause stability problems in some
-                    situations For instance, should a child process of a
-                    preforked MPM crash, at most one client connection is
-                    affected. However, if a threaded child crashes, all the
-                    threads in that process disappear, which means all the
-                    clients currently being served by that process will see
-                    their connection aborted. Additionally, there may be
-                    so-called "thread-safety" issues, especially with
-                    third-party libraries. In threaded applications, threads
-                    may access the same variables indiscriminately, not knowing
-                    whether a variable may have been changed by another thread.
-                </p>
-                <p>This has been a sore point within the PHP community. The PHP
-                    processor heavily relies on third-party libraries and
-                    cannot guarantee that all of these are thread-safe. The
-                    good news is that if you are running Apache on Linux, you
-                    can run PHP in the preforked MPM without fear of losing too
-                    much performance relative to the threaded option. 
-                </p>
-                
-                
-            
-            <h4><a name="Spinning Locks" id="Spinning Locks">Spinning Locks
-                </a></h4>
-                
-                <p>Apache httpd maintains an inter-process lock around its
-                    network listener. For all practical purposes, this means
-                    that only one httpd child process can receive a request at
-                    any given time. The other processes are either servicing
-                    requests already received or are 'camping out' on
-                    the lock, waiting for the network listener to become
-                    available. This process is best visualized as a revolving
-                    door, with only one process allowed in the door at any
-                    time. On a heavily loaded web server with requests arriving
-                    constantly, the door spins quickly and requests are
-                    accepted at a steady rate. On a lightly loaded web server,
-                    the process that currently "holds" the lock may
-                    have to stay in the door for a while, during which all the
-                    other processes sit idle, waiting to acquire the lock. At
-                    this time, the parent process may decide to terminate some
-                    children based on its <code>MaxSpareServers
-                    </code>
-                    directive. 
-                </p>
-                
-                
-            
-            <h4><a name="The Thundering Herd" id="The Thundering Herd">The Thundering Herd
-                </a></h4>
-                
-                <p>The function of the 'accept mutex' (as this
-                    inter-process lock is called) is to keep request reception
-                    moving along in an orderly fashion. If the lock is absent,
-                    the server may exhibit the Thundering Herd syndrome. 
-                </p>
-                <p>Consider an American Football team poised on the line of
-                    scrimmage. If the football players were Apache processes
-                    all team members would go for the ball simultaneously at
-                    the snap. One process would get it, and all the others
-                    would have to lumber back to the line for the next snap. In
-                    this metaphor, the accept mutex acts as the quarterback,
-                    delivering the connection "ball" to the
-                    appropriate player process. 
-                </p>
-                <p>Moving this much information around is obviously a lot of
-                    work, and, like a smart person, a smart web server tries to
-                    avoid it whenever possible. Hence the revolving door
-                    construction. In recent years, many operating systems,
-                    including Linux and Solaris, have put code in place to
-                    prevent the Thundering Herd syndrome. Apache recognizes
-                    this and if you run with just one network listener, meaning
-                    one virtual host or just the main server, Apache will
-                    refrain from using an accept mutex. If you run with
-                    multiple listeners (for instance because you have a virtual
-                    host serving SSL requests), it will activate the accept
-                    mutex to avoid internal conflicts. 
-                </p>
-                <p>
-                    You can manipulate the accept mutex with the <code>
-                        AcceptMutex
-                    </code>
-                    directive. Besides turning the accept mutex off, you can
-                    select the locking mechanism. Common locking mechanisms
-                    include fcntl, System V Semaphores and pthread locking. Not
-                    all are available on every platform, and their availability
-                    also depends on compile-time settings. The various locking
-                    mechanisms may place specific demands on system resources:
-                    manipulate them with care. 
-                </p>
-                <p>There is no compelling reason to disable the accept mutex.
-                    Apache automatically recognizes the single listener
-                    situation described above and knows if it is safe to run
-                    without mutex on your platform. 
-                </p>
-                
-                
-            
-        
-        <h3><a name="Tuning the Operating System" id="Tuning the Operating System">Tuning the Operating System
-            </a></h3>
-            
-            <p>People often look for the 'magic tune-up' that will
-                make their system perform four times as fast by tweaking just
-                one little setting. The truth is, present-day UNIX derivatives
-                are pretty well adjusted straight out of the box and there is
-                not a lot that needs to be done to make them perform optimally.
-                However, there are a few things that an administrator can do to
-                improve performance. 
-            </p>
-            
-            
-            <h4><a name="RAM and Swap Space" id="RAM and Swap Space">RAM and Swap Space
-                </a></h4>
-                
-                <p>The usual mantra regarding RAM is "more is
-                    better". As discussed above, unused RAM is put to good
-                    use as file system cache. The Apache processes get bigger
-                    if you load more modules, especially if you use modules
-                    that generate dynamic page content within the processes,
-                    like PHP and mod_perl. A large configuration file-with many
-                    virtual hosts-also tends to inflate the process footprint.
-                    Having ample RAM allows you to run Apache with more child
-                    processes, which allows the server to process more
-                    concurrent requests. 
-                </p>
-                <p>While the various platforms treat their virtual memory in
-                    different ways, it is never a good idea to run with less
-                    disk-based swap space than RAM. The virtual memory system
-                    is designed to provide a fallback for RAM, but when you
-                    don't have disk space available and run out of
-                    swappable memory, your machine grinds to a halt. This can
-                    crash your box, requiring a physical reboot for which your
-                    hosting facility may charge you. 
-                </p>
-                <p>Also, such an outage naturally occurs when you least want
-                    it: when the world has found your website and is beating a
-                    path to your door. If you have enough disk-based swap space
-                    available and the machine gets overloaded, it may get very,
-                    very slow as the system needs to swap memory pages to disk
-                    and back, but when the load decreases the system should
-                    recover. Remember, you still have <code>MaxClients
-                    </code>
-                    to keep things in hand. 
-                </p>
-                <p>Most unix-like operating systems use designated disk
-                    partitions for swap space. When a system starts up it finds
-                    all swap partitions on the disk(s), by partition type or
-                    because they are listed in the file <code>/etc/fstab
-                    </code>
-                    ,and automatically enables them. When adding a disk or
-                    installing the operating system, be sure to allocate enough
-                    swap space to accommodate eventual RAM upgrades.
-                    Reassigning disk space on a running system is a cumbersome
-                    process. 
-                </p>
-                <p>Plan for available hard drive swap space of at least twice
-                    your amount of RAM, perhaps up to four times in situations
-                    with frequent peaking loads. Remember to adjust this
-                    configuration whenever you upgrade RAM on your system. In a
-                    pinch, you can use a regular file as swap space. For
-                    instructions on how to do this, see the manual pages for
-                    the <code>mkswap
-                    </code>
-                    and <code>swapon
-                    </code>
-                    or <code>swap
-                    </code>
-                    programs. 
-                </p>
-                
-                
-            
-            <h4><a name="ulimit: Files and Processes" id="ulimit: Files and Processes">ulimit: Files and Processes
-                </a></h4>
-                
-                <p>Given a machine with plenty of RAM and processor capacity,
-                    you can run hundreds of Apache processes if necessary. . .
-                    and if your kernel allows it. 
-                </p>
-                <p>Consider a situation in which several hundred web servers
-                    are running; if some of these need to spawn CGI processes,
-                    the maximum number of processes would occur quickly. 
-                </p>
-                <p>However, you can change this limit with the command 
-                </p>
-                
-                <div class="example"><p><code>
-                    ulimit [-H|-S] -u [newvalue]
-                </code></p></div>
-                
-                <p>This must be changed before starting the server, since the
-                    new value will only be available to the current shell and
-                    programs started from it. In newer Linux kernels the
-                    default has been raised to 2048. On FreeBSD, the number
-                    seems to be the rather unusual 513. In the default user
-                    shell on this system, <code>csh
-                    </code>
-                    the equivalent is <code>limit
-                    </code>
-                    and works analogous the the Bourne-like <code>ulimit
-                    </code>
-                    :
-                </p>
-                
-                <div class="example"><p><code>
-                    limit [-h] maxproc [newvalue]
-                </code></p></div>
-                
-                <p>Similarly, the kernel may limit the number of open files per
-                    process. This is generally not a problem for pre-forked
-                    servers, which just handle one request at a time per
-                    process. Threaded servers, however, serve many requests per
-                    process and much more easily run out of available file
-                    descriptors. You can increase the maximum number of open
-                    files per process by running the 
-                </p>
-                
-                <div class="example"><p><code>ulimit -n [newvalue]
-                </code></p></div>
-                
-                <p>command. Once again, this must be done prior to starting
-                    Apache. 
-                </p>
-                
-                
-            
-            <h4><a name="Setting User Limits on System Startup" id="Setting User Limits on System Startup">Setting User Limits on System Startup
-                </a></h4>
-                
-                <p>Under Linux, you can set the ulimit parameters on bootup by
-                    editing the <code>/etc/security/limits.conf
-                    </code>
-                    file. This file allows you to set soft and hard limits on a
-                    per-user or per-group basis; the file contains commentary
-                    explaining the options. To enable this, make sure that the
-                    file <code>/etc/pam.d/login
-                    </code>
-                    contains the line 
-                </p>
-                
-                <div class="example"><p><code>session required /lib/security/pam_limits.so
-                </code></p></div>
-                
-                <p>All items can have a 'soft' and a 'hard'
-                    limit: the first is the default setting and the second the
-                    maximum value for that item. 
-                </p>
-                <p>
-                    In FreeBSD's <code>/etc/login.conf
-                    </code>
-                    these resources can be limited or extended system wide,
-                    analogously to <code>limits.conf
-                    </code>
-                    .'Soft' limits can be specified with <code>-cur
-                    </code>
-                    and 'hard' limits with <code>-max
-                    </code>
-                    .
-                </p>
-                <p>Solaris has a similar mechanism for manipulating limit
-                    values at boot time: In <code>/etc/system
-                    </code>
-                    you can set kernel tunables valid for the entire system at
-                    boot time. These are the same tunables that can be set with
-                    the <code>mdb
-                    </code>
-                    kernel debugger during run time. The soft and hard limit
-                    corresponding to ulimit -u can be set via: 
-                </p>
-                
-                <div class="example"><p><code>
-                    set rlim_fd_max=65536<br />
-                    set rlim_fd_cur=2048
-                </code></p></div>
-                
-                <p>Solaris calculates the maximum number of allowed processes
-                    per user (<code>maxuprc
-                    </code>
-                    )based on the total amount available memory on the system (<code>
-                        maxusers
-                    </code>
-                    ). You can review the numbers with 
-                </p>
-                
-                <div class="example"><p><code>sysdef -i | grep maximum
-                </code></p></div>
-                
-                <p>but it is not recommended to change them. 
-                </p>
-                
-                
-            
-            <h4><a name="Turn Off Unused Services and Modules" id="Turn Off Unused Services and Modules">Turn Off Unused Services and Modules
-                </a></h4>
-                
-                <p>Many UNIX and Linux distributions come with a slew of
-                    services turned on by default. You probably need few of
-                    them. For example, your web server does not need to be
-                    running sendmail, nor is it likely to be an NFS server,
-                    etc. Turn them off. 
-                </p>
-                <p>On Red Hat Linux, the chkconfig tool will help you do this
-                    from the command line. On Solaris systems <code>svcs
-                    </code>
-                    and <code>svcadm
-                    </code>
-                    will show which services are enabled and disable them
-                    respectively. 
-                </p>
-                <p>In a similar fashion, cast a critical eye on the Apache
-                    modules you load. Most binary distributions of Apache
-                    httpd, and pre-installed versions that come with Linux
-                    distributions, have their modules enabled through the <code>
-                        LoadModule
-                    </code>
-                    directive. 
-                </p>
-                <p>Unused modules may be culled: if you don't rely on
-                    their functionality and configuration directives, you can
-                    turn them off by commenting out the corresponding <code>
-                        LoadModule
-                    </code>
-                    lines. Read the documentation on each module&#8217;s
-                    functionality before deciding whether to keep it enabled.
-                    While the performance overhead of an unused module is
-                    small, it's also unnecessary. 
-                </p>
-                
-                
-            
-        
-    </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
-<div class="section">
-<h2><a name="Caching Content" id="Caching Content">Caching Content
-        </a></h2>
-        
-        <p>Requests for dynamically generated content usually take
-            significantly more resources than requests for static content.
-            Static content consists of simple filespages, images, etc.-on disk
-            that are very efficiently served. Many operating systems also
-            automatically cache the contents of frequently accessed files in
-            memory. 
-        </p>
-        <p>Processing dynamic requests, on the contrary, can be much more
-            involved. Running CGI scripts, handing off requests to an external
-            application server and accessing database content can introduce
-            significant latency and processing load to a busy web server. Under
-            many circumstances, performance can be improved by turning popular
-            dynamic requests into static requests. In this section, two
-            approaches to this will be discussed. 
-        </p>
-        
-        
-        <h3><a name="Making Popular Pages Static" id="Making Popular Pages Static">Making Popular Pages Static
-            </a></h3>
-            
-            <p>By pre-rendering the response pages for the most popular queries
-                in your application, you can gain a significant performance
-                improvement without giving up the flexibility of dynamically
-                generated content. For instance, if your application is a
-                flower delivery service, you would probably want to pre-render
-                your catalog pages for red roses during the weeks leading up to
-                Valentine's Day. When the user searches for red roses,
-                they are served the pre-rendered page. Queries for, say, yellow
-                roses will be generated directly from the database. The
-                mod_rewrite module included with Apache is a great tool to
-                implement these substitutions. 
-            </p>
-            
-            
-            <h4><a name="Example: A Statically Rendered Blog" id="Example: A Statically Rendered Blog">Example: A Statically Rendered Blog
-                </a></h4>
-                
-                <p>
-                    <strong>'we should provide a more useful example here.
-                        One showing how to make Wordpress or Drupal suck less.
-                    </strong>
-                    ' 
-                </p>
-                <p>Blosxom is a lightweight web log package that runs as a CGI.
-                    It is written in Perl and uses plain text files for entry
-                    input. Besides running as CGI, Blosxom can be run from the
-                    command line to pre-render blog pages. Pre-rendering pages
-                    to static HTML can yield a significant performance boost in
-                    the event that large numbers of people actually start
-                    reading your blog. 
-                </p>
-                <p>To run blosxom for static page generation, edit the CGI
-                    script according to the documentation. Set the $static dir
-                    variable to the <code>DocumentRoot
-                    </code>
-                    of the web server, and run the script from the command line
-                    as follows: 
-                </p>
-                
-                <div class="example"><p><code>$ perl blosxom.cgi -password='whateveryourpassword'
-                </code></p></div>
-                
-                <p>This can be run periodically from Cron, after you upload
-                    content, etc. To make Apache substitute the statically
-                    rendered pages for the dynamic content, we&#8217;ll use
-                    mod_rewrite. This module is included with the Apache source
-                    code, but is not compiled by default. It can be built with
-                    the server by passing the option <code>
-                        --enable-rewrite[=shared]
-                    </code>
-                    to the configure command. Many binary distributions of
-                    Apache come with mod_rewrite included. The following is an
-                    example of an Apache virtual host that takes advantage of
-                    pre-rendered blog pages: 
-                </p>
-                
-                <div class="example"><p><code>Listen *:8001<br />
-                    &lt;VirtualHost *:8001&gt;<br />
-                    <span class="indent">
-                        ServerName blog.sandla.org:8001<br />
-                        ServerAdmin sander@temme.net<br />
-                        DocumentRoot "/home/sctemme/inst/blog/httpd/htdocs"<br />
-                        &lt;Directory
-                        "/home/sctemme/inst/blog/httpd/htdocs"&gt;<br />
-                        <span class="indent">
-                            Options +Indexes<br />
-                            Order allow,deny<br />
-                            Allow from all<br />
-                            RewriteEngine on<br />
-                            RewriteCond %{REQUEST_FILENAME} !-f<br />
-                            RewriteCond %{REQUEST_FILENAME} !-d<br />
-                            RewriteRule ^(.*)$ /cgi-bin/blosxom.cgi/$1 [L,QSA]<br />
-                        </span>
-                        &lt;/Directory&gt;<br />
-                        RewriteLog
-                        /home/sctemme/inst/blog/httpd/logs/rewrite_log<br />
-                        RewriteLogLevel 9<br />
-                        ErrorLog /home/sctemme/inst/blog/httpd/logs/error_log<br />
-                        LogLevel debug<br />
-                        CustomLog /home/sctemme/inst/blog/httpd/logs/access_log
-                        common<br />
-                        ScriptAlias /cgi-bin/ /home/sctemme/inst/blog/bin/<br />
-                        &lt;Directory "/home/sctemme/inst/blog/bin"&gt;<br />
-                        <span class="indent">
-                            Options +ExecCGI<br />
-                            Order allow,deny<br />
-                            Allow from all<br />
-                        </span>
-                        &lt;/Directory&gt;<br />
-                    </span>
-                    &lt;/VirtualHost&gt;
-                </code></p></div>
-                
-                <p>
-                    The <code>RewriteCond
-                    </code>
-                    and <code>RewriteRule
-                    </code>
-                    directives say that, if the requested resource does not
-                    exist as a file or a directory, its path is passed to the
-                    Blosxom CGI for rendering. Blosxom uses Path Info to
-                    specify blog entries and index pages, so this means that if
-                    a particular path under Blosxom exists as a static file in
-                    the file system, the file is served instead. Any request
-                    that isn't pre- rendered is served by the CGI. This
-                    means that individual entries, which show the comments, are
-                    always served by the CGI which in turn means that your
-                    comment spam is always visible. This configuration also
-                    hides the Blosxom CGI from the user-visible URL in their
-                    Location bar. mod_rewrite is a fantastically powerful and
-                    versatile module: investigate it to arrive at a
-                    configuration that is best for your situation. 
-                </p>
-                
-                
-            
-        
-        <h3><a name="Caching Content With mod_cache" id="Caching Content With mod_cache">Caching Content With mod_cache
-            </a></h3>
-            
-            <p>The mod_cache module provides intelligent caching of HTTP
-                responses: it is aware of the expiration timing and content
-                requirements that are part of the HTTP specification. The
-                mod_cache module caches URL response content. If content sent
-                to the client is considered cacheable, it is saved to disk.
-                Subsequent requests for that URL will be served directly from
-                the cache. The provider module for mod_cache, mod_disk_cache,
-                determines how the cached content is stored on disk. Most
-                server systems will have more disk available than memory, and
-                it's good to note that some operating system kernels cache
-                frequently accessed disk content transparently in memory, so
-                replicating this in the server is not very useful. 
-            </p>
-            <p>To enable efficient content caching and avoid presenting the
-                user with stale or invalid content, the application that
-                generates the actual content has to send the correct response
-                headers. Without headers like <code>Etag:
-                </code>
-                ,<code>Last-Modified:
-                </code>
-                or <code>Expires:
-                </code>
-                ,mod_cache can not make the right decision on whether to cache
-                the content, serve it from cache or leave it alone. When
-                testing content caching, you may find that you need to modify
-                your application or, if this is impossible, selectively disable
-                caching for URLs that cause problems. The mod_cache modules are
-                not compiled by default, but can be enabled by passing the
-                option <code>--enable-cache[=shared]
-                </code>
-                to the configure script. If you use a binary distribution of
-                Apache httpd, or it came with your port or package collection,
-                it may have mod_cache already included. 
-            </p>
-            
-            
-            <h4><a name="Example: wiki.apache.org" id="Example: wiki.apache.org">Example: wiki.apache.org
-                </a></h4>
-                
-                <p>
-                    <strong>'Is this still the case? Maybe we should give
-                        a better example here too.
-                    </strong>
-                </p>
-                <p>
-                    The Apache Software Foundation Wiki is served by <a href="/httpd/MoinMoin">
-                        MoinMoin
-                    </a>
-                    .<a href="/httpd/MoinMoin">MoinMoin
-                    </a>
-                    is written in Python and runs as a CGI. To date, any
-                    attempts to run it under mod_python has been unsuccessful.
-                    The CGI proved to place an untenably high load on the
-                    server machine, especially when the Wiki was being indexed
-                    by search engines like Google. To lighten the load on the
-                    server machine, the Apache Infrastructure team turned to
-                    mod_cache. It turned out <a href="/httpd/MoinMoin">MoinMoin
-                    </a>
-                    needed a small patch to ensure proper behavior behind the
-                    caching server: certain requests can never be cached and
-                    the corresponding Python modules were patched to send the
-                    proper HTTP response headers. After this modification, the
-                    cache in front of the Wiki was enabled with the following
-                    configuration snippet in <code>httpd.conf
-                    </code>
-                    :
-                </p>
-                
-                <div class="example"><p><code>
-                    CacheRoot /raid1/cacheroot<br />
-                    CacheEnable disk /<br />
-                    # A page modified 100 minutes ago will expire in 10 minutes<br />
-                    CacheLastModifiedFactor .1<br />
-                    # Always check again after 6 hours<br />
-                    CacheMaxExpire 21600
-                </code></p></div>
-                
-                <p>This configuration will try to cache any and all content
-                    within its virtual host. It will never cache content for
-                    more than six hours (the <code>CacheMaxExpire
-                    </code>
-                    directive). If no <code>Expires:
-                    </code>
-                    header is present in the response, mod_cache will compute
-                    an expiration period from the <code>Last-Modified:
-                    </code>
-                    header. The computation using <code>CacheLastModifiedFactor
-                    </code>
-                    is based on the assumption that if a page was recently
-                    modified, it is likely to change again in the near future
-                    and will have to be re-cached. 
-                </p>
-                <p>
-                    Do note that it can pay off to <em>disable
-                    </em>
-                    the <code>ETag:
-                    </code>
-                    header: For files smaller than 1k the server has to
-                    calculate the checksum (usually MD5) and then send out a <code>
-                        304 Not Modified
-                    </code>
-                    response, which will take waste some CPU and still saturate
-                    the same amount of network resources for the transfer (one
-                    TCP packet). For resources larger than 1k it might prove
-                    CPU expensive to calculate the header for each request.
-                    Unfortunately there does currently not exist a way to cache
-                    these headers. 
-                </p>
-                <div class="example"><p><code>
-                    &lt;FilesMatch \.(jpe?g|png|gif|js|css|x?html|xml)&gt;<br />
-                    <span class="indent">
-                        FilesETag None<br />
-                    </span>
-                    &lt;/FilesMatch&gt;
-                </code></p></div>
-                
-                <p>
-                    This will disable the generation of the <code>ETag:
-                    </code>
-                    header for most static resources. The server does not
-                    calculate these headers for dynamic resources. 
-                </p>
-                
-                
-            
-        
-    </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
-<div class="section">
-<h2><a name="Further Considerations" id="Further Considerations">Further Considerations
-        </a></h2>
-        
-        <p>Armed with the knowledge of how to tune a sytem to deliver the
-            desired the performance, we will soon discover that <em>one
-            </em>
-            system might prove a bottleneck. How to make a system fit for
-            growth, or how to put a number of systems into tune will be
-            discussed in <a href="/httpd/PerformanceScalingOut">
-                PerformanceScalingOut
-            </a>
-            .
-        </p>
-    </div></div>
-<div class="bottomlang">
-<p><span>Available Languages: </span><a href="../en/misc/perf-scaling.html" title="English">&nbsp;en&nbsp;</a></p>
-</div><div id="footer">
-<p class="apache">Copyright 2012 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>

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