[systemd-devel] question on special configuration case

[Hebenstreit, Michael]

Sorry for directing this question here, but I did not find any mailing list that would be a better fit.

Problem: I'm running an HPC benchmarking cluster. We are evaluating RH7/CentOS7/OL7 and have a problem with system noise generated by the systemd components (v 219-19.0.2, see below). 

Background: All cores of the CPU (up to 288) are utilized 99.99% by the application. Because of the tight coupling node to node (of programs running on 200+ nodes) every time an OS process wakes up this automatically delays EVERY process on EVERY node. As those small interruptions are not synchronized over the cluster, the overall effect on the effective performance is "time of the single delay" times "number of nodes in the job". Therefore we need to keep the OS of our systems are stripped down to an absolute bare minimum.

a) we have no use for any type of logging. The only log we have is kernel dmesg
b) there is only a single user at any time on the system (logging in via ssh).
c) The only demons running are those necessary for NFS, ntp and sshd. 
d) we do not run Gnome or similar desktop.

Goal: For these reasons we want to shut down dbus-daemon, systemd-journald, systemd-logind and after startup also systemd-udevd. In our special case they do not serve any purpose. Unfortunately the basic configuration options do not allow this.

Questions: 
	Can you provide any guidance?
	Will PID 1 (systemd) continue to do its work (first tests were already successful)?
	What are security implications when shutting down systemd-logind?
	Is there any mailing list better suited you can point me too?


Thanks for any help you can provide
Michael





Installed:
	systemd-networkd-219-19.0.2.el7_2.9.x86_64
	systemd-219-19.0.2.el7_2.9.x86_64
	systemd-devel-219-19.0.2.el7_2.9.x86_64
	systemd-sysv-219-19.0.2.el7_2.9.x86_64
	systemd-libs-219-19.0.2.el7_2.9.x86_64
	systemd-python-219-19.0.2.el7_2.9.x86_64
	systemd-resolved-219-19.0.2.el7_2.9.x86_64

------------------------------------------------------------------------
Michael Hebenstreit                 Senior Cluster Architect
Intel Corporation, MS: RR1-105/H14  Software and Services Group/DCE
4100 Sara Road                      Tel.:   +1 505-794-3144 
Rio Rancho, NM 87124
UNITED STATES                       E-mail: michael.hebenstreit at intel.com