Op ma 14 jun. 2021 om 17:29 schreef Ronny Meeus <ronny.meeus@xxxxxxxxx>: > > Hello > > I want to use cgroups to control my heavy cpuload consuming applications. > All apps are running in the realtime domain and I'm using kernel 4.9 > and cgroup v1. > > I created a small application that monitors the CPU load (by reading > the /proc filesystem) and when it enters a full load condition, I > dynamically start to put the high consuming processes into a cgroup > (which were created during system start-up). Each process will have > it's own cgroup created under the root-cgroup. > > The budget I assign to the process is equal to the budget it has > consumed in the previous measurement interval (for example 5s). As > long as the load continues to be high, I start to gradually reduce the > budget of the cgroup until the system is idle enough. > > This works reasonably well, but in some cases I see that a very high > load consuming application is stopped completely at the moment it is > put in a cgroup, although the budget allocated to it is correctly > calculated based on the load it consumed in my previous interval. > > An example: > - cpu.rt_period_us = 1000000 > - cpu.rt_runtime_us = 400000 > I would assume that an application put in a cgroup with this > configuration can consume 40% of the CPU and it actually does. But > sometimes, immediately after the process assignment, it stops for a > short period (something like 1 or 2s) and then starts to consume 40% > again. > > Is that expected behavior? > > It looks like the "budget" it has consumed in the root-cgroup is taken > into account when it is moved to its own group and this results in the > stall. > > Best regards, > Ronny Note that this is a dual-core CPU and the process that is doing the cgroup updates is running in a single thread. So that other core will most probably running the application that is moved into the child cgroup.
