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The systemd System and Service Manager
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Auke Kok 94243ef299 readahead: chunk on spinning media
Readahead has all sorts of bad side effects depending on your
storage media. On rotating disks, it may be degrading startup
performance if enough requests are queued spanning linearly
over all blocks early at boot, and mount, blkid and friends
want to insert reads to the start of these block devices after.

The end result is that on spinning disks with ext3/4 that udev
and mounts take a very long time, and nothing really happens until
readahead is completely finished.

This has the net effect that the CPU is almost entirely idle
for the entire period that readahead is working. We could have
finished starting up quite a lot of services in this time if
we were smarter at how we do readahead.

This patch sorts all requests into 2 second "chunks" and sub-sorts
each chunk by block. This adds a single cross-drive seek per "chunk"
but has the benefit that we will have a lot of the blocks we need
early on in the boot sequence loaded into memory faster.

For a comparison of how before/after bootcharts look (ext4 on a
mobile 5400rpm 250GB drive) please look at:

    http://foo-projects.org/~sofar/blocked-tests/

There are bootcharts in the "before" and "after" folders where you
should be able to see that many low-level services finish 5-7
seconds earlier with the patch applied (after).
2013-03-26 10:32:32 -07:00
catalog catalog: remove broken links to wiki 2013-03-19 21:50:43 -04:00
docs doc: disable gtk-doc test again - you are a really annoying piece of software 2013-03-21 15:07:54 +01:00
hwdb hwdb: ID_PRODUCT_FROM_DATABASE --> ID_MODEL_FROM_DATABASE 2013-03-23 16:38:21 +01:00
keymaps keymaps: Use F20 for micmute keys to be friendly to X.org 2013-03-19 13:12:00 +01:00
keymaps-force-release keymap: Update the list of Samsung Series 9 models 2012-11-28 21:27:03 +01:00
m4 Replace autoconf int max test with simple define 2013-01-22 23:20:15 -05:00
man man: document that the passive units cannot be pulled in mnaully 2013-03-26 15:24:44 +01:00
po l10n: Updated Polish translation 2013-01-14 23:30:39 +01:00
rules Drop trailing whitespace 2013-03-22 22:51:52 +01:00
shell-completion Drop trailing whitespace 2013-03-22 22:51:52 +01:00
src readahead: chunk on spinning media 2013-03-26 10:32:32 -07:00
sysctl.d sysctl: default - add safe sysrq options 2013-03-15 19:30:53 +01:00
test test: test irreversible jobs 2013-02-23 14:18:17 +01:00
tmpfiles.d Make PrivateTmp dirs also inaccessible from the outside 2013-03-20 14:08:41 -04:00
units units: disallow manual starting of passive units 2013-03-26 15:15:39 +01:00
.dir-locals.el Keep emacs configuration in one configuration file. 2011-03-08 01:53:46 +01:00
.gitignore shared: add simple priority queue implementation 2013-03-21 02:54:47 +01:00
.mailmap Add a few entries to .mailmap 2013-01-29 21:31:41 -05:00
.vimrc add .vimrc 2012-01-23 04:42:11 +01:00
autogen.sh build-sys: use _FORTIFY_SOURCE only if optimizing 2013-01-11 10:03:16 -05:00
CODING_STYLE analyze: various cleanups 2013-03-08 18:58:08 +01:00
configure.ac build-sys: bump version and .so revisions 2013-03-26 15:43:43 +01:00
DISTRO_PORTING build-sys: fix spelling of sysvrcndir 2013-01-08 02:37:37 +01:00
introspect.awk
LICENSE.GPL2 relicense to LGPLv2.1 (with exceptions) 2012-04-12 00:24:39 +02:00
LICENSE.LGPL2.1 licence: remove references to old FSF address 2012-12-17 11:41:31 +01:00
LICENSE.MIT relicense to LGPLv2.1 (with exceptions) 2012-04-12 00:24:39 +02:00
make-directive-index.py man: use lxml for faster generation and pretty printing 2013-03-09 08:47:50 -05:00
make-man-index.py man: use lxml for faster generation and pretty printing 2013-03-09 08:47:50 -05:00
make-man-rules.py build-sys: generate links for html alias pages 2013-03-09 08:47:50 -05:00
Makefile-man.am build-sys: generate links for html alias pages 2013-03-09 08:47:50 -05:00
Makefile.am readahead: chunk on spinning media 2013-03-26 10:32:32 -07:00
NEWS NEWS: tweak grammar 2013-03-26 11:56:01 -04:00
README man: use lxml for faster generation and pretty printing 2013-03-09 08:47:50 -05:00
TODO build-sys: bump version and .so revisions 2013-03-26 15:43:43 +01:00

systemd System and Service Manager

DETAILS:
        http://0pointer.de/blog/projects/systemd.html

WEB SITE:
        http://www.freedesktop.org/wiki/Software/systemd

GIT:
        git://anongit.freedesktop.org/systemd/systemd
        ssh://git.freedesktop.org/git/systemd/systemd

GITWEB:
        http://cgit.freedesktop.org/systemd/systemd

MAILING LIST:
        http://lists.freedesktop.org/mailman/listinfo/systemd-devel
        http://lists.freedesktop.org/mailman/listinfo/systemd-commits

IRC:
        #systemd on irc.freenode.org

BUG REPORTS:
        https://bugs.freedesktop.org/enter_bug.cgi?product=systemd

AUTHOR:
        Lennart Poettering
        Kay Sievers
        ...and many others

LICENSE:
        LGPLv2.1+ for all code
        - except sd-daemon.[ch] and sd-readahead.[ch] which are MIT
        - except src/udev/ which is (currently still) GPLv2+

REQUIREMENTS:
        Linux kernel >= 2.6.39
          CONFIG_DEVTMPFS
          CONFIG_CGROUPS (it's OK to disable all controllers)
          CONFIG_INOTIFY_USER
          CONFIG_SIGNALFD
          CONFIG_TIMERFD
          CONFIG_EPOLL
          CONFIG_NET
          CONFIG_SYSFS

        Linux kernel >= 3.8 for Smack support

        Udev will fail to work with the legacy layout:
          CONFIG_SYSFS_DEPRECATED=n

        Legacy hotplug slows down the system and confuses udev:
          CONFIG_UEVENT_HELPER_PATH=""

        Userspace firmware loading is deprecated, will go away, and
        sometimes causes problems:
          CONFIG_FW_LOADER_USER_HELPER=n

        Some udev rules and virtualization detection relies on it:
          CONFIG_DMIID

        Mount and bind mount handling might require it:
          CONFIG_FHANDLE

        Optional but strongly recommended:
          CONFIG_IPV6
          CONFIG_AUTOFS4_FS
          CONFIG_TMPFS_POSIX_ACL
          CONFIG_TMPFS_XATTR
          CONFIG_SECCOMP

        For systemd-bootchart a kernel with procfs support and several
        proc output options enabled is required:
          CONFIG_PROC_FS
          CONFIG_SCHEDSTATS
          CONFIG_SCHED_DEBUG

        For UEFI systems:
          CONFIG_EFI_VARS
          CONFIG_EFI_PARTITION

        dbus >= 1.4.0
        libcap
        libblkid >= 2.20 (from util-linux) (optional)
        libkmod >= 5 (optional)
        PAM >= 1.1.2 (optional)
        libcryptsetup (optional)
        libaudit (optional)
        libacl (optional)
        libattr (optional)
        libselinux (optional)
        liblzma (optional)
        tcpwrappers (optional)
        libgcrypt (optional)
        libqrencode (optional)
        libmicrohttpd (optional)
        libpython (optional)
        make, gcc, and similar tools

        During runtime you need the following additional dependencies:

        util-linux >= v2.19 (requires fsck -l, agetty -s)
        sulogin (from util-linux >= 2.22 or sysvinit-tools, optional but recommended)
        dracut (optional)
        PolicyKit (optional)

        When building from git you need the following additional dependencies:

        docbook-xsl
        xsltproc
        automake
        autoconf
        libtool
        intltool
        gperf
        gtkdocize (optional)
        python (optional)
        sphinx (optional)
        python-lxml (entirely optional)

        When systemd-hostnamed is used it is strongly recommended to
        install nss-myhostname to ensure that in a world of
        dynamically changing hostnames the hostname stays resolvable
        under all circumstances. In fact, systemd-hostnamed will warn
        if nss-myhostname is not installed.

        Note that D-Bus can link against libsystemd-login.so, which
        results in a cyclic build dependency. To accommodate for this
        please build D-Bus without systemd first, then build systemd,
        then rebuild D-Bus with systemd support.

        To build HTML documentation for python-systemd using sphinx,
        please first install systemd (using 'make install'), and then
        invoke sphinx-build with 'make sphinx-<target>', with <target>
        being 'html' or 'latexpdf'. If using DESTDIR for installation,
        pass the same DESTDIR to 'make sphinx-html' invocation.

USERS AND GROUPS:
        Default udev rules use the following standard system group
        names, which need to be resolvable by getgrnam() at any time,
        even in the very early boot stages, where no other databases
        and network are available:

        tty, dialout, kmem, video, audio, lp, floppy, cdrom, tape, disk

        During runtime the journal daemon requires the
        "systemd-journal" system group to exist. New journal files will
        be readable by this group (but not writable) which may be used
        to grant specific users read access.

        It is also recommended to grant read access to all journal
        files to the system groups "wheel" and "adm" with a command
        like the following in the post installation script of the
        package:

        # setfacl -nm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/

        The journal gateway daemon requires the
        "systemd-journal-gateway" system user and group to
        exist. During execution this network facing service will drop
        privileges and assume this uid/gid for security reasons.

WARNINGS:
        systemd will warn you during boot if /etc/mtab is not a
        symlink to /proc/mounts. Please ensure that /etc/mtab is a
        proper symlink.

        systemd will warn you during boot if /usr is on a different
        file system than /. While in systemd itself very little will
        break if /usr is on a separate partition many of its
        dependencies very likely will break sooner or later in one
        form or another. For example udev rules tend to refer to
        binaries in /usr, binaries that link to libraries in /usr or
        binaries that refer to data files in /usr. Since these
        breakages are not always directly visible systemd will warn
        about this, since this kind of file system setup is not really
        supported anymore by the basic set of Linux OS components.

        For more information on this issue consult
        http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken

        To run systemd under valgrind, compile with VALGRIND defined
        (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
        false positives will be triggered by code which violates
        some rules but is actually safe.