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I am trying to setup a kubernetes cluster on a raspberry pi cluster using Ubuntu 20.04.3. In many online guides available, one of the steps is mentioned as follows:

Edit the /boot/firmware/cmdline.txt and add cgroup_enable=cpuset cgroup_enable=memory cgroup_memory=1 swapaccount=1 at the end.

The above step is mentioned without any explanation. So, to check my current configuration (without applying the above boot config) I run /proc/cgroups which gives me the following output:

#subsys_name    hierarchy       num_cgroups     enabled
cpuset  8       1       1
cpu     4       43      1
cpuacct 4       43      1
blkio   7       43      1
memory  0       51      0
devices 10      43      1
freezer 3       2       1
net_cls 2       1       1
perf_event      5       1       1
net_prio        2       1       1
pids    6       48      1
rdma    9       1       1

Since swap needs to be disabled, I have checked it is already disabled. As such I have the following questions:

  1. I believe in the output that cpuset is enabled since it has the value of 1 for the enabled column. Am I correct? If so, is explicitly setting cgroup_enable=cpuset necessary?
  2. Since the value under enabled is 0 for memory I believe it is not enabled. Am I correct? If so, what does cgroup_enable=memory and cgroup_memory=1 do? Why do I have to set both of them?
  3. What is the purpose of setting swapaccount=1? Does it make sense to set it if swap is disabled anyway?

cgroups is a new topic to me and as such I would like to know better what each of the commands do instead of blindly copying them.

EDIT: I went through the kernel source code and noticed that nothing called cgroup_memory exists. Yes a function exists by that name but it binds to a command cgroup.memory. So, are all the online blogs talking about cgroup_memory just copied a typo as is?

Sayak Mukhopadhyay
  • 181

1 Answers1

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For 2, it seems that both flags are specific to the Raspberry Pi Linux kernel. The cgroup_memory=1 is probably not necessary anymore, it is meant as a backwards compatibility flag. So as long as cgroup_memory=0 is not present, cgroup_enable=memory should be good enough. This comment in the Raspberry Pi bug tracker is suggesting that.

falstaff
  • 965