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The systemd System and Service Manager
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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). |
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catalog | ||
docs | ||
hwdb | ||
keymaps | ||
keymaps-force-release | ||
m4 | ||
man | ||
po | ||
rules | ||
shell-completion | ||
src | ||
sysctl.d | ||
test | ||
tmpfiles.d | ||
units | ||
.dir-locals.el | ||
.gitignore | ||
.mailmap | ||
.vimrc | ||
autogen.sh | ||
CODING_STYLE | ||
configure.ac | ||
DISTRO_PORTING | ||
introspect.awk | ||
LICENSE.GPL2 | ||
LICENSE.LGPL2.1 | ||
LICENSE.MIT | ||
make-directive-index.py | ||
make-man-index.py | ||
make-man-rules.py | ||
Makefile-man.am | ||
Makefile.am | ||
NEWS | ||
README | ||
TODO |
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.