[Bug 1972159] Re: systemd-oomd frequently kills firefox and visual studio code

[Łukasz Zemczak]

The SRU looked good so I accepted it into -proposed, since this
basically seems the current consensus regarding the systemd-oomd
situation in jammy. It's a behavioral change, but is not viable to call
a 'regression'.

Note to SRU members: let's make sure that the kinetic counterpart gets
staged before this is released into -updates.

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https://bugs.launchpad.net/bugs/1972159

Title:
  systemd-oomd frequently kills firefox and visual studio code

Status in systemd package in Ubuntu:
  Confirmed
Status in systemd source package in Jammy:
  Fix Committed
Status in systemd source package in Kinetic:
  Confirmed
Status in systemd package in Fedora:
  Unknown

Bug description:
  [Impact]

  The "swap kill" side of systemd-oomd has caused unexpected behavior
  for desktop users. A user's browser, desktop session, or some other
  desktop application may be killed by systemd-oomd when SwapUsedLimit
  is reached, but system performance otherwise appears unaffected. This
  leaves users confused as to why their application was killed, and has
  a negative impact on their desktop experience.

  For now, let's disable the swap kill functionality by default.

  [Test Plan]

  On Jammy desktop, check the ManagedOOMSwap property on -.slice:

  $ systemctl show -- "-.slice" | grep "^ManagedOOMSwap"
  ManagedOOMSwap=kill # After the fix, this should print ManagedOOMSwap=auto

  [Where problems could occur]

  Disabling swap kill by default means that users may experience
  degraded system performance due to high swap usage, because systemd-
  oomd will no longer act on cgroups with high swap usage.

  [Other Info]

  If a user wishes to restore the original systemd-oomd behavior, they
  can do so by creating the following overrides file:

   $ cat /etc/systemd/system/-.slice.d/10-oomd-root-slice-defaults.conf
   [Slice]
   ManagedOOMSwap=kill

  [Original Description]

  Since I installed Ubuntu 22.04, firefox and visual studio code are
  frequently killed by systemd-oomd (every 2hours).

  I have 8 GB memory and never experienced this before the upgrade to
  Ubuntu 22.04. I thus assume that the claim that there is not enough
  memory is abusive. Did 64GB of memory become the minimum requirement
  to run Ubuntu ?

  The second problem is that it gives a very bad user experience which
  is critical for new Ubuntu users.

  There should be a warning prior killing apps to give the opportunity
  to save the app data. There should at least be an apologize and an
  explanation after killing the app.

  The current behavior gives the impression that Ubuntu 22.04 is
  unreliable and unsafe to use which is a problem for an LTS release
  that many people might want to use for critical production context.

  There might be a configuration problem with systemd-oomd or simply a
  bogus behavior. I would recommend to disable it or remove it
  completely until this problem is resolved. This is what I will do for
  myself because I have work to do.

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