mirror of
https://github.com/systemd/systemd.git
synced 2024-11-02 02:21:44 +03:00
204 lines
9.2 KiB
XML
204 lines
9.2 KiB
XML
<?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>
|