systemd/postmarketos-base-systemd: enable systemd-oomd by default

This enables systemd-oomd by default and provides some default
configuration for system.slice and for all slices that run under user.

This default slice config is inspired by what Fedora ships,
which seems like a sensible default for us to start with. Units/slices
within these two top-ish level slices can set their own limits and
actions if they want.

extra-repos/systemd/postmarketos-base-systemd/APKBUILD

@@ -2,7 +2,7 @@
 # Co-maintainer: Clayton Craft <clayton@craftyguy.net>
 # pmbootstrap installs this, if systemd is selected in "pmbootstrap init".
 pkgname=postmarketos-base-systemd
-pkgver=27
+pkgver=28
 pkgrel=0
 pkgdesc="Meta package for running postmarketOS with systemd"
 url="https://postmarketos.org"
@@ -40,7 +40,9 @@ _source644="
 	etc/systemd/logind.conf
 	usr/share/mkinitfs/files-extra/01-initramfs-base-systemd.files
 	usr/lib/systemd/system-preset/90-base.preset
+	usr/lib/systemd/system/system.slice.d/10-oomd-defaults.conf
 	usr/lib/systemd/user-preset/90-base.preset
+	usr/lib/systemd/user/slice.d/10-oomd-defaults.conf
 "
 
 _source755="
@@ -73,7 +75,9 @@ sha512sums="
 fbaa33425e507062a454f11bda48508f261c2144e5c23a20f567dc1cef14ce1dec57f8d934f418f5b6095509757f8503481aba9790a04c8f9f6995e65833d8c9  rootfs-etc-profile.d-99motd.sh
 2faac294bb632762e247b850f09ff4b544ccff6c462efd8d4faca71ba30bdfa9c460377a0dc88e92c5dbbe251017d164064a56ac0e0410f224b45d4f5f81866c  rootfs-etc-systemd-logind.conf
 15423bfda57c90ab62fe69865ca4072a0aeb83bf77d9c278257e346f4da81843d010b41003c91ae9f3fcb1c67447645e7c19078eea2bf11312051e6ad7523ad1  rootfs-usr-share-mkinitfs-files-extra-01-initramfs-base-systemd.files
-0e30cad5ab3a84807c406b66e391bf4c420d40c763fdb768a8194a499b91a705c18233921ad62d2d201de3fe3386e970cfddf55c38b6ba42fd565322ab51fe5e  rootfs-usr-lib-systemd-system-preset-90-base.preset
+5fcf8119413bd5990f99c6045105ec8f160263e572cd9cc871c002408636e663d8bc7d86e937fb488b43e99bfbee1609039fb02fdebf60b91fb329f062cf521e  rootfs-usr-lib-systemd-system-preset-90-base.preset
+1458d526e3d68c052126f648a33c3f22af10e3a4d479dded824c2b18b2022b43232ea6f8c2061f051927b2d612750017a2ecf7e1a19680b71ca2dc112d5bd3f6  rootfs-usr-lib-systemd-system-system.slice.d-10-oomd-defaults.conf
 c7ec5a4e7c7dcbf855f34e80adb225f52221340099216e57792b04f07e7b367e004209551e9a74152d9212926aba1b1a0a2680d3c2e35f15cca6f3cf0c9a3841  rootfs-usr-lib-systemd-user-preset-90-base.preset
+1458d526e3d68c052126f648a33c3f22af10e3a4d479dded824c2b18b2022b43232ea6f8c2061f051927b2d612750017a2ecf7e1a19680b71ca2dc112d5bd3f6  rootfs-usr-lib-systemd-user-slice.d-10-oomd-defaults.conf
 605df1f004783d2e0ec5dd99a688bca27502c8c24bc05fb4dc26589b2070b0fbd1cf9bd56e6861d7cda2f8ac8147e7eb040acfd886185c01c8cf9de8b1ce2dcd  rootfs-usr-bin-setup-timezone
 "

extra-repos/systemd/postmarketos-base-systemd/rootfs-usr-lib-systemd-system-preset-90-base.preset

@@ -27,6 +27,7 @@ enable tinydm.service
 enable udisks2.service
 enable cups.service
 enable zram_swap.service
+enable systemd-oomd.service
 
 # Note: technically these two shouldn't be enabled at the same time, but
 # pmos-base-wifi provides should make sure that only one is installed at the

extra-repos/systemd/postmarketos-base-systemd/rootfs-usr-lib-systemd-system-system.slice.d-10-oomd-defaults.conf

+[Slice]
+ManagedOOMSwap=kill
+ManagedOOMMemoryPressure=kill
+ManagedOOMMemoryPressureLimit=80%

extra-repos/systemd/postmarketos-base-systemd/rootfs-usr-lib-systemd-user-slice.d-10-oomd-defaults.conf

+[Slice]
+ManagedOOMSwap=kill
+ManagedOOMMemoryPressure=kill
+ManagedOOMMemoryPressureLimit=80%