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Diffstat (limited to 'man/systemd-readahead-replay.service.xml')
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diff --git a/man/systemd-readahead-replay.service.xml b/man/systemd-readahead-replay.service.xml new file mode 100644 index 0000000000..e37b1a9edf --- /dev/null +++ b/man/systemd-readahead-replay.service.xml @@ -0,0 +1,113 @@ +<?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"> + + <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>systemd 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> + <para><filename>/usr/lib/systemd/systemd-readahead</filename></para> + </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 disk 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 + preceeding 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>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |