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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:45:08 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:45:08 -0500 |
| commit | e8ec7aa8e38a93f5b034ac74cebce5de23710317 (patch) | |
| tree | aa031937bf856c1f8d6ad7877b8d2cb0224da5ef /rubbos/app/httpd-2.0.64/docs/manual/misc/descriptors.html.en | |
| parent | cc40af334e619bb549038238507407866f774f8f (diff) | |
upload http
JIRA: BOTTLENECK-10
Change-Id: I7598427ff904df438ce77c2819ee48ac75ffa8da
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
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diff --git a/rubbos/app/httpd-2.0.64/docs/manual/misc/descriptors.html.en b/rubbos/app/httpd-2.0.64/docs/manual/misc/descriptors.html.en new file mode 100644 index 00000000..005356d6 --- /dev/null +++ b/rubbos/app/httpd-2.0.64/docs/manual/misc/descriptors.html.en @@ -0,0 +1,233 @@ +<?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>Descriptors and Apache - 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 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 2.0</p> +<img alt="" src="../images/feather.gif" /></div> +<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> +<div id="path"> +<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.0</a> > <a href="./">Miscellaneous Documentation</a></div><div id="page-content"><div id="preamble"><h1>Descriptors and Apache</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/misc/descriptors.html" title="English"> en </a></p> +</div> + + + <div class="warning"><h3>Warning:</h3> + <p>This document has not been fully updated + to take into account changes made in the 2.0 version of the + Apache HTTP Server. Some of the information may still be + relevant, but please use it with care.</p> + </div> + + <p>A <em>descriptor</em>, also commonly called a <em>file + handle</em> is an object that a program uses to read or write + an open file, or open network socket, or a variety of other + devices. It is represented by an integer, and you may be + familiar with <code>stdin</code>, <code>stdout</code>, and + <code>stderr</code> which are descriptors 0, 1, and 2 + respectively. Apache needs a descriptor for each log file, plus + one for each network socket that it listens on, plus a handful + of others. Libraries that Apache uses may also require + descriptors. Normal programs don't open up many descriptors at + all, and so there are some latent problems that you may + experience should you start running Apache with many + descriptors (<em>i.e.</em>, with many virtual hosts).</p> + + <p>The operating system enforces a limit on the number of + descriptors that a program can have open at a time. There are + typically three limits involved here. One is a kernel + limitation, depending on your operating system you will either + be able to tune the number of descriptors available to higher + numbers (this is frequently called <em>FD_SETSIZE</em>). Or you + may be stuck with a (relatively) low amount. The second limit + is called the <em>hard resource</em> limit, and it is sometimes + set by root in an obscure operating system file, but frequently + is the same as the kernel limit. The third limit is called the + <em>soft resource</em> limit. The soft limit is always less + than or equal to the hard limit. For example, the hard limit + may be 1024, but the soft limit only 64. Any user can raise + their soft limit up to the hard limit. Root can raise the hard + limit up to the system maximum limit. The soft limit is the + actual limit that is used when enforcing the maximum number of + files a process can have open.</p> + + <p>To summarize:</p> + +<div class="example"><p><code> + #open files <= soft limit <= hard limit <= kernel limit +</code></p></div> + + + <p>You control the hard and soft limits using the + <code>limit</code> (csh) or <code>ulimit</code> (sh) + directives. See the respective man pages for more information. + For example you can probably use <code>ulimit -n + unlimited</code> to raise your soft limit up to the hard limit. + You should include this command in a shell script which starts + your webserver.</p> + + <p>Unfortunately, it's not always this simple. As mentioned + above, you will probably run into some system limitations that + will need to be worked around somehow. Work was done in version + 1.2.1 to improve the situation somewhat. Here is a partial list + of systems and workarounds (assuming you are using 1.2.1 or + later).</p> + + </div> +<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#bsdi">BSDI 2.0</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#freebsd">FreeBSD 2.2, BSDI 2.1+</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#linux">Linux</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#solaris">Solaris through 2.5.1</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#AIX">AIX</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#sco">SCO OpenServer</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#tru64">Compaq Tru64 UNIX/Digital UNIX/OSF</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#others">Others</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="bsdi" id="bsdi">BSDI 2.0</a></h2> + + <p>Under BSDI 2.0 you can build Apache to support more + descriptors by adding <code>-DFD_SETSIZE=nnn</code> to + <code>EXTRA_CFLAGS</code> (where nnn is the number of + descriptors you wish to support, keep it less than the hard + limit). But it will run into trouble if more than + approximately 240 Listen directives are used. This may be + cured by rebuilding your kernel with a higher + FD_SETSIZE.</p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="freebsd" id="freebsd">FreeBSD 2.2, BSDI 2.1+</a></h2> + + <p>Similar to the BSDI 2.0 case, you should define + <code>FD_SETSIZE</code> and rebuild. But the extra Listen + limitation doesn't exist.</p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="linux" id="linux">Linux</a></h2> + + <p>By default Linux has a kernel maximum of 256 open + descriptors per process. There are several patches available + for the 2.0.x series which raise this to 1024 and beyond, and + you can find them in the "unofficial patches" section of <a href="http://www.linuxhq.com/">the Linux Information HQ</a>. + None of these patches are perfect, and an entirely different + approach is likely to be taken during the 2.1.x development. + Applying these patches will raise the FD_SETSIZE used to + compile all programs, and unless you rebuild all your + libraries you should avoid running any other program with a + soft descriptor limit above 256. As of this writing the + patches available for increasing the number of descriptors do + not take this into account. On a dedicated webserver you + probably won't run into trouble.</p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="solaris" id="solaris">Solaris through 2.5.1</a></h2> + + <p>Solaris has a kernel hard limit of 1024 (may be lower in + earlier versions). But it has a limitation that files using + the stdio library cannot have a descriptor above 255. Apache + uses the stdio library for the ErrorLog directive. When you + have more than approximately 110 virtual hosts (with an error + log and an access log each) you will need to build Apache + with <code>-DHIGH_SLACK_LINE=256</code> added to + <code>EXTRA_CFLAGS</code>. You will be limited to + approximately 240 error logs if you do this.</p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="AIX" id="AIX">AIX</a></h2> + + <p>AIX version 3.2?? appears to have a hard limit of 128 + descriptors. End of story. Version 4.1.5 has a hard limit of + 2000.</p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="sco" id="sco">SCO OpenServer</a></h2> + + <p>Edit the <code>/etc/conf/cf.d/stune</code> file or use + <code>/etc/conf/cf.d/configure</code> choice 7 (User and + Group configuration) and modify the <code>NOFILES</code> + kernel parameter to a suitably higher value. SCO recommends a + number between 60 and 11000, the default is 110. Relink and + reboot, and the new number of descriptors will be + available.</p> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="tru64" id="tru64">Compaq Tru64 UNIX/Digital UNIX/OSF</a></h2> + + <ol> + <li>Raise <code>open_max_soft</code> and + <code>open_max_hard</code> to 4096 in the proc subsystem. + Do a man on sysconfig, sysconfigdb, and + sysconfigtab.</li> + + <li>Raise <code>max-vnodes</code> to a large number which + is greater than the number of apache processes * 4096 + (Setting it to 250,000 should be good for most people). + Do a man on sysconfig, sysconfigdb, and + sysconfigtab.</li> + + <li>If you are using Tru64 5.0, 5.0A, or 5.1, define + <code>NO_SLACK</code> to work around a bug in the OS. + <code>CFLAGS="-DNO_SLACK" ./configure</code></li> + </ol> + + </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="others" id="others">Others</a></h2> + + <p>If you have details on another operating system, please + submit it through our <a href="http://httpd.apache.org/bug_report.html">Bug Report + Page</a>.</p> + + <p>In addition to the problems described above there are + problems with many libraries that Apache uses. The most common + example is the bind DNS resolver library that is used by pretty + much every unix, which fails if it ends up with a descriptor + above 256. We suspect there are other libraries that similar + limitations. So the code as of 1.2.1 takes a defensive stance + and tries to save descriptors less than 16 for use while + processing each request. This is called the <em>low slack + line</em>.</p> + + <p>Note that this shouldn't waste descriptors. If you really + are pushing the limits and Apache can't get a descriptor above + 16 when it wants it, it will settle for one below 16.</p> + + <p>In extreme situations you may want to lower the low slack + line, but you shouldn't ever need to. For example, lowering it + can increase the limits 240 described above under Solaris and + BSDI 2.0. But you'll play a delicate balancing game with the + descriptors needed to serve a request. Should you want to play + this game, the compile time parameter is + <code>LOW_SLACK_LINE</code> and there's a tiny bit of + documentation in the header file <code>httpd.h</code>.</p> + + <p>Finally, if you suspect that all this slack stuff is causing + you problems, you can disable it. Add <code>-DNO_SLACK</code> + to <code>EXTRA_CFLAGS</code> and rebuild. But please report it + to our <a href="http://httpd.apache.org/bug_report.html">Bug + Report Page</a> so that we can investigate. </p> + + </div></div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/misc/descriptors.html" title="English"> en </a></p> +</div><div id="footer"> +<p class="apache">Copyright 2009 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> +<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></div> +</body></html>
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