+++ /dev/null
-<?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="systemd-readahead-replay.service" conditional='ENABLE_READAHEAD'
- xmlns:xi="http://www.w3.org/2001/XInclude">
-
- <refentryinfo>
- <title>systemd-readahead-replay.service</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>systemd-readahead-replay.service</refentrytitle>
- <manvolnum>8</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>systemd-readahead-replay.service</refname>
- <refname>systemd-readahead-collect.service</refname>
- <refname>systemd-readahead-done.service</refname>
- <refname>systemd-readahead-done.timer</refname>
- <refname>systemd-readahead</refname>
- <refpurpose>Disk read ahead logic</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <para><filename>systemd-readahead-replay.service</filename></para>
- <para><filename>systemd-readahead-collect.service</filename></para>
- <para><filename>systemd-readahead-done.service</filename></para>
- <para><filename>systemd-readahead-done.timer</filename></para>
- <cmdsynopsis>
- <command>/usr/lib/systemd/systemd-readahead/systemd-readahead</command>
- <arg choice="opt" rep="repeat">OPTIONS</arg>
- <arg choice="plain">COMMAND</arg>
- <arg choice="opt">DIRECTORY | FILE</arg>
- </cmdsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><filename>systemd-readahead-collect.service</filename>
- is a service that collects disk usage patterns at boot
- time. <filename>systemd-readahead-replay.service</filename>
- is a service that replays this access data collected
- at the subsequent boot. Since disks tend to be
- magnitudes slower than RAM, this is intended to improve
- boot speeds by pre-loading early at boot all data on
- disk that is known to be read for the complete boot
- process.</para>
-
- <para><filename>systemd-readahead-done.service</filename>
- is executed a short while after boot completed and signals
- <filename>systemd-readahead-collect.service</filename>
- to end data collection. On this signal, this service
- will then sort the collected disk accesses and store
- information about them in
- <filename>/.readahead</filename>.</para>
-
- <para>Normally, both
- <filename>systemd-readahead-collect.service</filename>
- and
- <filename>systemd-readahead-replay.service</filename>
- are activated at boot so that access patterns from the
- preceding boot are replayed and new data collected
- for the subsequent boot. However, on read-only media
- where the collected data cannot be stored, it might
- be a good idea to disable
- <filename>systemd-readahead-collect.service</filename>.</para>
-
- <para>On rotating media, when replaying disk accesses
- at early boot,
- <filename>systemd-readahead-replay.service</filename>
- will order read requests by their location on disk. On
- non-rotating media, they will be ordered by their
- original access timestamp. If the file system supports
- it,
- <filename>systemd-readahead-collect.service</filename>
- will also defragment and rearrange files on disk to
- optimize subsequent boot times.</para>
- </refsect1>
-
- <refsect1>
- <title>Options</title>
-
- <para><filename>systemd-readahead</filename> understands
- the following options:</para>
-
- <variablelist>
- <varlistentry>
- <term><option>--files-max=</option></term>
-
- <listitem><para>Maximum number of
- files to read ahead. Only valid
- for thes <command>collect</command>
- command.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>--file-size-max=</option></term>
-
- <listitem><para>Maximum size of files
- in bytes to read ahead. Only valid
- for the <command>collect</command>
- and <command>replay</command>
- commands.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>--timeout=</option></term>
-
- <listitem><para>Maximum time in microseconds
- to spend collecting data. Only valid
- for the <command>collect</command>
- command.</para></listitem>
- </varlistentry>
-
- <xi:include href="standard-options.xml" xpointer="help" />
- <xi:include href="standard-options.xml" xpointer="version" />
- </variablelist>
-
- </refsect1>
-
- <refsect1>
- <title>Commands</title>
-
- <para>The following commands are understood by
- <filename>systemd-readahead</filename>:</para> <variablelist>
- <varlistentry>
- <term><command>collect
- [<replaceable>DIRECTORY</replaceable>]</command></term>
- <listitem>
- <para>Collect read-ahead data on
- early boot. When terminating, it will
- write out a pack file to the indicated
- directory containing the read-ahead
- data. </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><command>replay
- [<replaceable>DIRECTORY</replaceable>]</command></term>
- <listitem>
- <para>Perform read-ahead on the
- specified directory tree.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><command>analyze
- [<replaceable>FILE</replaceable>]</command></term>
- <listitem>
- <para>Dumps the content of the
- read-ahead pack file to the
- terminal. For each file, the
- output lists approximately how
- much will be read ahead by
- the <command>replay</command>
- command.</para>
- </listitem>
- </varlistentry>
-
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- </para>
- </refsect1>
-
-</refentry>
~ianmdlvl / elogind.git / blobdiff