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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd-readahead" conditional='ENABLE_READAHEAD'>
<refentryinfo>
<title>sd-readahead</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd-readahead</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd-readahead</refname>
<refpurpose>Reference implementation of APIs for
controlling boot-time read-ahead</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include "sd-readahead.h"</funcsynopsisinfo>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><filename>sd-readahead.c</filename> and
<filename>sd-readahead.h</filename> provide a
reference implementation for APIs for controlling boot-time
read-ahead, as implemented by the read-ahead subsystem
of the
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
init system.</para>
<para>See
<citerefentry><refentrytitle>sd_readahead</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for more information about the function
implemented.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>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.</para>
<para>In addition, for details about the algorithms
check the liberally licensed reference implementation
sources:
<ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/readahead/sd-readahead.c"/>
and <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-readahead.h"/></para>
<para>These APIs are implemented in the reference
implementation's drop-in
<filename>sd-readahead.c</filename> and
<filename>sd-readahead.h</filename> 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.</para>
<para>The functions provided by this interface become
NOPs when -DDISABLE_SYSTEMD is set during
compilation. In addition, if
<filename>sd-readhead.c</filename> is compiled on
non-Linux systems it becomes NOPs.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_readahead</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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