[Bug 1966381] Re: applications crash that never crashed under Ubuntu-20.04

[Nick Rosbrook]

In the near term, we could consider tweaking the systemd-oomd defaults
in Ubuntu. According to the commit that added systemd-oomd in Jammy [1],
the current config is based on Fedora's. This includes using the default
value of SwapUsedLimit=90% [2]. However, Fedora has more swap space by
default: a fresh install of Fedora 35 in a VM with 4GB of memory has 4GB
of swap, whereas a fresh install of Jammy in a VM with 4GB of memory has
968MB of swap. So, maybe the default SwapUsedLimit is not appropriate
for Ubuntu.

[1] https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?h=ubuntu-jammy&id=771fee9e73316c92e065e93946ec64c578b43706
[2] https://www.freedesktop.org/software/systemd/man/oomd.conf.html#SwapUsedLimit=

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https://bugs.launchpad.net/bugs/1966381

Title:
  applications crash that never crashed under Ubuntu-20.04

Status in systemd package in Ubuntu:
  New
Status in systemd source package in Jammy:
  New

Bug description:
  Just now I was watching some video in Firefox. I popped over to
  another virtual workspace for a few minutes, and when I popped back to
  Firefox it had gone. The same thing had been happening all week (I
  installed fresh Ubuntu-22.04 last week) with Chrome, Firefox and
  Thunderbird.

  This time instead of shrugging it off I looked in the logs, and found
  this

  Mar 25 19:45:40 ubuntu systemd-oomd[960]: Killed /user.slice/user-1001.slice/user at 1001.service/app.slice/app-gnome-firefox-6607.scope due to memory used (15940579328) / total (16153944064) and swap used (925564928) / total (1023406080) being more than 90.00%
  Mar 22 08:11:29 ubuntu systemd[5029]: app-gnome-google\x2dchrome-5412.scope: systemd-oomd killed 298 process(es) in this unit.
  Mar 23 11:09:28 ubuntu systemd-oomd[1055]: Killed /user.slice/user-1001.slice/user at 1001.service/app.slice/app-gnome-thunderbird-5418.scope due to memory used (15591993344) / total (16149745664) and swap used (927760384) / total (1023406080) being more than 90.00%
  Mar 23 11:09:28 ubuntu systemd[5029]: app-gnome-thunderbird-5418.scope: systemd-oomd killed 173 process(es) in this unit.

  I know it's saying those three entirely unrelated applications had
  suddenly decided to swallow all the RAM+swap on this laptop of mine -
  but the very same apps didn't act like that last week under
  Ubuntu-20.04, so I suspect something else is going on

  I can't say they hadn't swallowed all the RAM, but there is ZERO sign
  of a system on the verge of collapsing - everything has been screaming
  along just nicely - no sign of the "staggering" you normally get when
  the OS is heavily into swap.

  However, now that I look I see my 16G laptop only has 1G swap??? I
  just let the Ubuntu installer do it's defaults - but it used to auto-
  choose 1xRAM or 2xRAM - what's with this 1G swap? Could that be
  related?

  ProblemType: Bug
  DistroRelease: Ubuntu 22.04
  Package: systemd-oomd 249.11-0ubuntu1
  ProcVersionSignature: Ubuntu 5.15.0-23.23-generic 5.15.27
  Uname: Linux 5.15.0-23-generic x86_64
  ApportVersion: 2.20.11-0ubuntu79
  Architecture: amd64
  CasperMD5CheckResult: pass
  CurrentDesktop: ubuntu:GNOME
  Date: Fri Mar 25 19:47:44 2022
  InstallationDate: Installed on 2022-03-13 (11 days ago)
  InstallationMedia: Ubuntu 22.04 LTS "Jammy Jellyfish" - Alpha amd64 (20220313)
  SourcePackage: systemd
  UpgradeStatus: No upgrade log present (probably fresh install)

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