f2561e85982ed25b610cad6253599a051f9ec8e2Lennart Poettering<?xml version='1.0'?> <!--*-nxml-*-->

f2561e85982ed25b610cad6253599a051f9ec8e2Lennart Poettering<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"

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f2561e85982ed25b610cad6253599a051f9ec8e2Lennart Poettering

<refentry id="sd-daemon">

<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>7</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/plain/src/readahead/sd-readahead.c"/>

resp. <ulink url="http://cgit.freedesktop.org/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>7</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>