QA:Testcase Swap Based Killing

Description

This test case tests that systemd-oomd kills the largest swap consumer when swap used is greater 90% (or whatever limit was defined by systemd-oomd-defaults).

Setup

• This test case should be performed on either bare-metal or virtual machines.
• Check that you are running systemd 248~rc1 or higher with systemctl --version.
• Ensure the systemd-oomd-defaults package is installed (included with Fedora 34).
• Boot the system and log in as a regular user.
• Ensure no other conflicting userspace OOM killers are running. For example you may have to stop earlyoom:

sudo systemctl stop earlyoom

• So as not to trigger the memory pressure policy for systemd-oomd, create an override with the following commands (don't forget to remove this file and systemctl daemon-reload to restore the settings afterwards):

sudo mkdir /etc/systemd/system/user@.service.d/
printf "[Service]\nManagedOOMMemoryPressure=auto" | sudo tee /etc/systemd/system/user@.service.d/99-test.conf
sudo systemctl daemon-reload

How to test

• Check that systemd-oomd is running:

systemctl status systemd-oomd

• Check that the systemd-oomd-defaults policy was applied by running oomctl and verifying that "/" is listed as a path under "Swap Monitored CGroups" along with the current swap usage.
• Now run the test:

systemd-run --user -r --unit systoomd_swap_test tail /dev/zero

• Make sure to clean up the override and reset the test unit after verifying the results:

sudo rm /etc/systemd/system/user@.service.d/99-test.conf
sudo systemctl daemon-reload
systemctl --user reset-failed systoomd_swap_test.service

Expected Results

• systemd-oomd will have killed the unit started above.
• You can verify by checking for some of the relevant log lines with journalctl: "Swap used <...> is more than 90%" or "systemd-oomd killed <...> process(es)"
• The output of systemctl --user status systoomd_swap_test should say the unit is killed (with no mention of oom-kill).
• Swap used should be below 90% (use free -h)