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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd-readahead</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 215</span><hr><div class="refentry"><a name="sd-readahead"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd-readahead — Reference implementation of APIs for
controlling boot-time read-ahead</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include "sd-readahead.h"</pre></div></div><div class="refsect1"><a name="idm214198772224"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="filename">sd-readahead.c</code> and
<code class="filename">sd-readahead.h</code> provide a
reference implementation for APIs for controlling boot-time
read-ahead, as implemented by the read-ahead subsystem
of the
<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>
init system.</p><p>See
<a href="sd_readahead.html"><span class="citerefentry"><span class="refentrytitle">sd_readahead</span>(3)</span></a>
for more information about the function
implemented.</p></div><div class="refsect1"><a name="idm214198767552"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>This interface is provided by the reference
implementation of APIs for controlling boot-time
read-ahead and distributed with the systemd
package. The algorithms it implements are simple, and
can easily be reimplemented in daemons if it is
important to support this interface without using the
reference implementation. See the respective function
man pages for details.</p><p>In addition, for details about the algorithms,
check the liberally licensed reference implementation
sources:
<a class="ulink" href="http://cgit.freedesktop.org/systemd/systemd/plain/src/readahead/sd-readahead.c" target="_top">http://cgit.freedesktop.org/systemd/systemd/plain/src/readahead/sd-readahead.c</a>
and <a class="ulink" href="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-readahead.h" target="_top">http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-readahead.h</a></p><p>These APIs are implemented in the reference
implementation's drop-in
<code class="filename">sd-readahead.c</code> and
<code class="filename">sd-readahead.h</code> files. It is
recommended that applications consuming these APIs copy
the implementation into their source tree, either
verbatim or in excerpts. These interfaces are
currently not available in a dynamic library.</p><p>The functions provided by this interface become
NOPs when -DDISABLE_SYSTEMD is set during
compilation. In addition, if
<code class="filename">sd-readhead.c</code> is compiled on
non-Linux systems it becomes NOPs.</p></div><div class="refsect1"><a name="idm214198760976"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
<a href="sd_readahead.html"><span class="citerefentry"><span class="refentrytitle">sd_readahead</span>(3)</span></a>,
<a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>
</p></div></div></body></html>
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