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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>2. Native Posix Thread Library vs LinuxThreads</title><link rel="stylesheet" href="docbook.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="PowerDNS manual" /><link rel="up" href="performance.html" title="Chapter 9. Authoritative Server Performance" /><link rel="prev" href="performance.html" title="Chapter 9. Authoritative Server Performance" /><link rel="next" href="performance-settings.html" title="3. Performance related settings" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2. Native Posix Thread Library vs LinuxThreads</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="performance.html">Prev</a> </td><th width="60%" align="center">Chapter 9. Authoritative Server Performance</th><td width="20%" align="right"> <a accesskey="n" href="performance-settings.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="2. Native Posix Thread Library vs LinuxThreads"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="nptl"></a>2. Native Posix Thread Library vs LinuxThreads</h2></div></div></div><p>
To get the best performance under Linux, especially on SMP
systems, the use of NPTL is advised. The difference in
performance can be over a factor of ten in some circumstances.
</p><p>
NPTL is the default library on modern Linux distributions, so
there is generally not a problem, except if you use a
statically compiled version that, for portability reasons,
defaults to LinuxThreads. This includes all .deb and .rpm files
provided by us up to and including 2.9.18.
</p><p>
When running a PowerDNS-provided static binary of 2.9.18 or
lower, it may make sense to recompile, or to upgrade to a
newer version, if available. When recompiling, be sure to use
a supported compiler, like g++ >3.2. You might also consider
moving to a distribution supplied version.
</p><p>
A good indication that your installation might benefit from
such an upgrade is to watch the 'cs' count in the output of
vmstat 1. If this is very high (> 10000), you are suffering
from a LinuxThreads performance problem called 'overspin'.
</p><p>
Thanks are due to L. Bunt Jackson who noted the static
compilation problem in an article in Dr. Dobb's Journal.
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