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I dockerized a component that follows a process model. The master process forks itself many times. I want to establish a cgroup hierarchy inside the docker container to vary the CPU and memory limit on a per process basis.
Is there a way I can do this without using '--privileged' or 'CAP_SYTEM_ADMIN'?
Is there a way I can make the cgroup that the container belongs to as the root of the cgroup subsytem that I am implementing for the processes? (Divide the resources allocated to the container among the processes).
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So basically you use cgroups to control how much of a given key resource (CPU, memory, network, and disk I/O) can be accessed or used by a process or set of processes. Cgroups are a key component of containers because there are often multiple processes running in a container that you need to control together.
Cgroups make each container use a fair share of CPU relative to the other containers. This prevents oversubscription on the host VM where one or more containers hog the CPU and leave no computing resources to the others. The way cgroups allocate CPU time is based on shares.
Docker supports cgroup v2 since Docker 20.10. Running Docker on cgroup v2 also requires the following conditions to be satisfied: containerd: v1. 4 or later.
Control groups (cgroups) Cgroups are fundamental blocks of making a container. A cgroup allocates and limits resources such as CPU, memory, network I/O that are used by containers. The container engine automatically creates a cgroup filesystem of each type, and sets values for each container when the container is run.
The conclusion that I came to was that there is no current solution for this since Docker does not support cgroup virtualization nor does the Linux kernel. We need some form of cgroup virtualization in order to implement cgroups inside a container.
lxc does this using a FUSE based solution called lxcfs : https://linuxcontainers.org/lxcfs/introduction/
Also, there is a kernel patch that supports cgroup namespaces which as far as I can see have not been approved : https://lwn.net/Articles/605903/.
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