infra/common/cgroups.nix

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# Relatively inspired by fbtax2:
# https://facebookmicrosites.github.io/cgroup2/docs/fbtax-results.html
#
# See also the Chris Down talk at LISA'21:
# https://www.usenix.org/conference/lisa21/presentation/down
{ ... }:
let
systemCriticalSliceConfig = {
ManagedOOMMemoryPressure = "kill";
# guarantee availability of memory
MemoryMin = "192M";
# default 100
IOWeight = 1000;
# default 100
CPUWeight = 1000;
};
in
{
systemd.oomd = {
enable = true;
# why not, we have cgroups at user level now so it'll just kill the
# terminal
enableRootSlice = true;
enableSystemSlice = true;
enableUserSlices = true;
};
systemd.enableCgroupAccounting = true;
systemd.services.nix-daemon = {
serviceConfig = {
# FIXME: how do i deprioritize this for memory
CPUWeight = 10;
IOWeight = 10;
};
};
systemd.slices.hostcritical = {
description = "Ensures that services to keep the system alive remain alive";
unitConfig = {
# required to avoid a dependency cycle on systemd-oomd. systemd will
# actually guess this right but we should fix it anyway.
DefaultDependencies = false;
};
sliceConfig = systemCriticalSliceConfig;
};
# make root logins higher priority for resources
systemd.slices."user-0" = {
sliceConfig = systemCriticalSliceConfig;
};
systemd.slices.system = {
sliceConfig = {
ManagedOOMMemoryPressure = "kill";
ManagedOOMMemoryPressureLimit = "50%";
IOWeight = 100;
};
};
systemd.services.sshd = {
serviceConfig = {
Slice = "hostcritical.slice";
};
};
systemd.services.systemd-oomd = {
serviceConfig = {
Slice = "hostcritical.slice";
};
};
systemd.services.systemd-journald = {
serviceConfig = {
Slice = "hostcritical.slice";
};
};
}