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