On Tue, 07.06.16 15:13, Hebenstreit, Michael (michael.hebenstr...@intel.com) wrote:
> 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. This is simply not supported on systemd. Systems without journald and udevd are explicitly not supported, and systems without dbus-daemon are only really supported for early boot schemes. You can of course ignore what we support and what not, but of course, then you really should know what you do, and you are basically on your own. Note that you can connect the journal to kmsg, if you like, and turn off local storage, via ForwardToKMsg= and Storage= in journald.conf. > Questions: > Can you provide any guidance? > Will PID 1 (systemd) continue to do its work (first tests were > already successful)? No, it will not. The only daemon of those listed you can realistically do without is logind, and if you do that, then you basically roll your own distro. > What are security implications when shutting down > systemd-logind? Well, there's no tracking of sessions anymore, i.e. polkit and all that stuff won't work anymore reasonably, and everything else that involves anything graphical and so on. If I were you I'd actually look what wakes up the system IRL instead of just trying to blanket remove everything. If you do that, then you are going to have to invest a lot of time dealing with the fallout yourself. Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
