Hi Keith Lofstrom!
On 2015.02.13 at 23:06:02 -0800, Keith Lofstrom wrote next:
> Well, hm. My questions about systemd (some may be hard to measure):
Why hard?
>
> 1) Does systemd use a LOT more RAM, like > 200MB, that cannot swap out?
# ps_mem |grep systemd
516.0 KiB + 60.0 KiB = 576.0 KiB systemd-logind
2.3 MiB + 65.5 KiB = 2.3 MiB systemd-udevd
3.6 MiB + 402.0 KiB = 4.0 MiB systemd
10.1 MiB + 3.7 MiB = 13.8 MiB systemd-journald
# cat /proc/meminfo |grep Mlocked
Mlocked: 0 kB
systemd uses about 7 MB of RAM. journal uses about 14 MB of RAM. None of
it is memlocked, so it can be swapped out.
> 2) Does systemd use a LOT more CPU cycles, slowing down user performance?
$ ps aux|grep -e systemd -e journal|grep -v dbus|grep -v grep
root 1 0.0 0.0 53244 5712 ? Ss янв29 0:56 /usr/lib/systemd/systemd --switched-root --system --deserialize 23
root 496 0.0 0.2 97172 19052 ? Ss янв29 0:32 /usr/lib/systemd/systemd-journald
root 508 0.0 0.0 45184 3272 ? Ss янв29 0:05 /usr/lib/systemd/systemd-udevd
root 943 0.0 0.0 34684 1556 ? Ss янв29 0:15 /usr/lib/systemd/systemd-logind
Over the course of time (15 days uptime), all parts of systemd and
journal use 0.0% of CPU on average.
One might claim that "systemd uses 0.04% CPU which is ten times more
than upstart which uses 0.004% CPU" or something but it certainly can't
slow down user performance at all. It speeds up service start and makes
reboot VERY fast. In fact, before systemd I had no idea my servers can
reboot that fast. Unless they have VMs to stop, they actually reboot like
1-2 seconds after "reboot" command - despite tons of services running.
They also boot within 30-50 seconds after grub, something that took 2
minutes before. Certainly, boot times aren't significant on server but
when whole reboot takes 2 minutes instead of former 5 minutes, it IS
very pleasant for people who have to interrupt all that they were doing
for just 2 minutes instead of 5.
> 3) Will systemd require Gnome 3/4/5/..N to manage properly?
I don't even know what do you mean, systemd has nothing to do with
graphics environment, you can manage every aspect of it on server
without X, from text mode. In fact, I'm unaware of any graphical
instruments to manage it, documentation only explains console commands
and config files.
(only backward dependency exists - some gnome 3 features require systemd
to work)
> 4) Can systemd /var/log files (or equivalent) be logrotated?
Not quite.
It rotates automatically based on settings in /etc/systemd/journald.conf
(size-based rotation or time-based rotation, by default it's
size-rotated since journal has built-in date filter, and entries are
compressed, so time-based rotation might create very uneven files).
If you desire, you can change settings and restart
systemd-journald.service - it will read new settings on start and rotate
according to them, if they say so.
You could force rotation from logrotate, of course, but it seems pointless.
--
Vladimir
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