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Harald Hoyer
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content/2013/11/13/_index.md
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content/2013/11/13/_index.md
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content/2013/11/13/fedora-boot-optimization.md
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content/2013/11/13/fedora-boot-optimization.md
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title = "Fedora Boot Optimization"
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date = 2013-11-13T10:12:04+00:00
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This article shows how to reduce boot time for Fedora 17, but the recipe can also be applied to 18, 19 and 20.
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The target is to get a fast booting system with NetworkManager running and gdm displaying the login
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screen as fast as possible.
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<!-- more -->
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The system I use here is a Lenovo T420s (2x2x Intel(R) Core(TM) i5-2540M CPU @ 2.60GHz)
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with an INTEL SSDSA2BW160G3L harddrive.
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First we choose a manual disk layout and use primary partitions and format them with ext4.
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In my case this results in:
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```sda1 ext4 /boot
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sda2 swap
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sda3 ext4
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```
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After the first boot, setup of the user, etc. and 2 reboots (always reboot 2 times,
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before taking the measurement, because readahead needs to adapt to the changed boot process).
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First we update everything.
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```console
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$ sudo yum update
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```
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After the reboots, I get:
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```console
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$ systemd-analyze
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Startup finished in 1413ms (kernel) + 2911ms (initramfs) + 10593ms (userspace) = 14918ms
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```
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Because I don't use any LVM, RAID or encrypted devices, I can safely turn off all nearly all
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`fedora-\*storage\*` services. To turn off these services, we use the `systemctl mask` command.
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A bonus with that mechanism is, that no rpm %post script turns them on automatically.
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```console
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$ cd /lib/systemd/system
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$ for i in fedora*storage* lvm2-monitor.* mdmonitor*.*; \
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do sudo systemctl mask $i; \
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done
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```
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On Fedora 17, it seems there are still some SysV initscripts left, so we turn them off:
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```console
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$ for i in livesys livesys-late spice-vdagentd;\
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do sudo chkconfig $i off;\
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done
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```
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Seems like we saved half of the time in userspace:
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```console
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$ systemd-analyze
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Startup finished in 1640ms (kernel) + 6556ms (userspace) = 8197ms
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```
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From now on, you really have to know what you are doing and how to revert your actions.
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To compare Fedora with e.g. Ubuntu, I will now turn off all services except NetworkManager.
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The result will be a Linux system without mail, firewall, printing, the abrt tools, avahi,
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some mountpoints, rsyslog, irqbalance, and selinux security.
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```console
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$ cd /lib/systemd/system
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$ for i in abrt*.service auditd.service avahi-daemon.* \
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bluetooth.* dev-hugepages.mount dev-mqueue.mount \
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fedora-configure.service fedora-loadmodules.service \
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fedora-readonly.service ip6tables.service \
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iptables.service irqbalance.service mcelog.service \
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rsyslog.service sendmail.service sm-client.service \
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sys-kernel-config.mount sys-kernel-debug.mount; do \
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sudo systemctl mask "$i"; \
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done
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```
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To disable selinux (only for measurements!), edit `/etc/selinux/config` and add `selinux=0`
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to the kernel command line.
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My `/etc/grub2.cfg` now looks like this:
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```
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linux /vmlinuz-3.3.7-1.fc17.x86_64 root=/dev/sda3 rootfstype=ext4 libahci.ignore_sss=1 raid=noautodetect selinux=0
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initrd /initramfs-3.3.7-1.fc17.x86_64.img
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```
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Now we are really fast!
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```console
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$ systemd-analyze
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Startup finished in 1329ms (kernel) + 1596ms (userspace) = 2926ms
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```
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I also like the idea of automounting (systemd's automount feature was an idea of mine :-).
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So I turn /boot in a "mount on demand" mountpoint. Also having /tmp as a tmpfs is one way to reduce
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disk activity (useful for e.g. a slow flash disk). My resulting /etc/fstab looks like this:
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```
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/dev/sda3 / ext4 defaults 1 1
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/dev/sda1 /boot ext4 noauto,comment=systemd.automount 1 2
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/dev/sda2 swap swap defaults 0 0
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tmpfs /tmp tmpfs defaults 0 0
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```
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This only saved a little bit of time, but still:
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```console
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$ systemd-analyze
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Startup finished in 1342ms (kernel) + 1426ms (userspace) = 2769ms
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```
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Because NetworkManager is started also by the graphical login target,
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I can remove it from the multi-user target and it will be started in parallel to the gdm login screen.
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```console
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$ sudo rm /etc/systemd/system/multi-user.target.wants/NetworkManager.service
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```
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This will shave of a few milliseconds:
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```console
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$ systemd-analyze
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Startup finished in 1323ms (kernel) + 1279ms (userspace) = 2603ms
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```
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To see the difference readahead makes for the system, I turn it off temporarily and reboot
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```console
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$ cd /lib/systemd/system
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$ for i in *readahead*; do sudo systemctl mask $i;done
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```
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Which will give us:
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```console
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$ systemd-analyze
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Startup finished in 1336ms (kernel) + 1210ms (userspace) = 2547ms
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```
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This time is a little bit misleading. Although it seems faster, the real time until the login screen
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is displayed is taking longer. So a fair comparison would involve a **stopwatch**.
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To turn off plymouth, because we want speed and not eye candy, I remove plymouth completely
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and regenerate the initramfs to get rid of it.
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```console
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$ sudo yum remove 'plymouth*'
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$ sudo dracut -f
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```
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After a reboot we get the stunning result of:
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```console
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$ systemd-analyze
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Startup finished in 612ms (kernel) + 499ms (initramfs) + 1330ms (userspace) = 2443ms
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```
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The nice thing about `systemctl mask` is, that you can always unmask it via `systemctl unmask`
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and only enable those default services, which you really need.
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Now, **turn selinux back on**, edit `/etc/selinux/config` and remove `selinux=0` from the kernel command line.
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You really don't want to trade some seconds for security!
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Have fun and happy rebooting!
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And don't forget to reboot twice to let the readahead optimization kick in!
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17
content/2013/11/13/linux-howto-get-the-number-of-cpus.md
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content/2013/11/13/linux-howto-get-the-number-of-cpus.md
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+++
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title = "Linux: HOWTO get the number of CPUs"
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date = 2013-11-13T12:13:04+00:00
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+++
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```console
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$ getconf _NPROCESSORS_ONLN
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```
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returns the number of CPUs online.
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<!-- more -->
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Internally it is parsing
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`/sys/devices/system/cpu/online`, which can have the contents: `0-3,5,7-9`.
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Better let getconf [do all the counting for you](https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/getsysstats.c#l127).
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This is very useful, if you want to optimize the number of threads.
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