[Bug 2139289] Re: Proposal: Enable systemd-oomd by Default in Ubuntu Desktop and Server

[Jeremy Bícha]

*** This bug is a duplicate of bug 1886314 ***
    https://bugs.launchpad.net/bugs/1886314

systemd-oomd is not installed by default for Ubuntu Server, but Ubuntu
Server is inherently a more minimal base system and it is expected that
system administrators will install the components they need.

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https://bugs.launchpad.net/bugs/2139289

Title:
  Proposal: Enable systemd-oomd by Default in Ubuntu Desktop and Server

Status in ubuntu-meta package in Ubuntu:
  Fix Released

Bug description:
  PROPOSAL: ENABLE SYSTEMD-OOMD BY DEFAULT IN UBUNTU DESKTOP AND SERVER

  Title:    Proposal: Enable systemd-oomd by Default in Ubuntu Desktop and Server
  Category: Desktop, Server

  ================================================================================

  SUMMARY

  I propose enabling systemd-oomd by default in Ubuntu Desktop and Ubuntu Server
  to improve system stability and responsiveness during memory pressure situations.

  ================================================================================

  PROBLEM

  When Ubuntu systems run low on memory, the kernel's OOM killer often responds
  too late, after the system has already become unresponsive.

  On Desktop:
  Users experience prolonged freezes where the desktop becomes unusable,
  sometimes requiring a hard reboot. This is a common pain point, especially
  on systems with 8GB RAM or less running memory-intensive workloads like
  browsers with many tabs, IDEs, or virtual machines.

  On Server:
  Memory exhaustion can lead to service degradation, failed health checks, and
  cascading failures. The kernel OOM killer may terminate critical services
  unpredictably, causing outages. Administrators often discover problems only
  after the damage is done.

  ================================================================================

  SOLUTION

  systemd-oomd is a userspace OOM killer that:

  * Acts proactively - monitors memory pressure via PSI (Pressure Stall
    Information) and intervenes before the system becomes unresponsive

  * Makes smarter decisions - uses cgroup information to kill the appropriate
    process rather than random selection

  * Provides better UX - keeps the desktop responsive during memory
  pressure

  * Improves server reliability - allows services to configure their own OOM
    policies via systemd unit options (ManagedOOMSwap=, ManagedOOMMemoryPressure=)

  * Enables graceful degradation - gives administrators control over which
    services are expendable vs. critical

  * Is mature and battle-tested - Fedora has shipped it by default since
    Fedora 34 (2021)

  ================================================================================

  SERVER-SPECIFIC BENEFITS

  * Granular control: Services can opt-in or opt-out via systemd unit
    configuration

  * Predictable behavior: Administrators can define which services should be
    killed first under memory pressure

  * Better observability: Actions are logged to the journal with clear
  reasoning

  * Container-aware: Works well with containerized workloads using
  cgroups v2

  * No external dependencies: Part of systemd, no additional monitoring stack
    required

  Example unit configuration:

    [Service]
    ManagedOOMMemoryPressure=kill
    ManagedOOMMemoryPressureLimit=80%

  ================================================================================

  PRECEDENT

  * Fedora Workstation: Enabled by default since version 34
  * Fedora Server: Enabled by default since version 34
  * systemd upstream: Actively maintained as part of the core systemd project

  ================================================================================

  TECHNICAL DETAILS

  * Package: systemd-oomd
  * Memory footprint: ~2MB RSS
  * Dependencies: Already satisfied on standard Ubuntu installations
  * Configuration: Works out of the box with sensible defaults
  * Requires: cgroups v2 (default in Ubuntu since 21.10)

  ================================================================================

  POTENTIAL CONCERNS

  Concern: Unexpected process termination
  Mitigation: systemd-oomd logs actions to the journal; users/admins can review
  what was killed and why

  Concern: Resource overhead
  Mitigation: Minimal (~2MB RAM); negligible compared to the benefit

  Concern: Conflicts with kernel OOM
  Mitigation: They complement each other; systemd-oomd acts first, kernel OOM
  remains as fallback

  Concern: Server workloads need stability
  Mitigation: Services can configure their own policies; critical services can
  opt-out

  Concern: Existing monitoring solutions
  Mitigation: systemd-oomd complements rather than replaces external monitoring

  ================================================================================

  REQUEST

  Consider including systemd-oomd in the default Ubuntu Desktop and Ubuntu Server
  installations, enabled by default.

  I'm happy to help with testing or provide additional information.

  ================================================================================

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