Hi,
I'm using RHEL7 with systemd-219-62.el7_6.6.x86_64. I've recently hit an issue whereby a process started by a systemd service cannot assign itself realtime priority. Digging into the issue it seems that it is because systemd starts all services within a cpu/system.slice/<service_name> cgroup which by default wont be allocated any rt runtime through the cpu.rt_runtime_us value.
I searched for info on how to solve this issue and came across https://www.freedesktop.org/wiki/Software/systemd/MyServiceCantGetRealtime/ unfortunately 2 of the 3 suggestions don't seem to be valid anymore:
-
/etc/systemd/system.conf and set DefaultControllers=This appears to have been removed as an option. When I tried this it had no effect
- edit your service file, and add ControlGroup=cpu:/ to its [Service] sectionThis doesn't appear to be a valid option anymore: https://bugzilla.redhat.com/show_bug.cgi?id=999986
This only leaves the option of setting cpu.rt_runtime_us value for the unit, however, there are a number of reasons why this isn't ideal and if the root cgroup config changes at any point then the value I choose isn't guaranteed to do what I had intended. (as pointed out in: https://lists.freedesktop.org/archives/systemd-devel/2015-March/029144.html)
Is there any other way to get my service to run within a cgroup that allows it to assign itself realtime priority? It would seem preferable to be able to just run the service in the root cgroup - is this possible through configuration?
Thanks
Jon
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