Feature 57 (config and provisioning): modules declare config and provisions, their files rendered from templates; synced with main (issues of feature 57, 874)

modules/memory-pressure/files/oomd.conf

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+# Managed by the mesh (module memory-pressure). Replaced on every push; edit the catalogue instead.
+#
+# systemd-oomd kills the worst unit before the kernel's OOM killer freezes the machine: when swap is
+# 90 % used, or when a watched unit stalls on memory for 20 s above its limit.
+[OOM]
+SwapUsedLimit=90%
+DefaultMemoryPressureLimit=60%
+DefaultMemoryPressureDurationSec=20s

modules/memory-pressure/files/root-slice.conf

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+# Managed by the mesh (module memory-pressure). Replaced on every push; edit the catalogue instead.
+#
+# systemd-oomd may act on swap exhaustion across the whole machine.
+[Slice]
+ManagedOOMSwap=kill

modules/memory-pressure/files/sysctl.conf

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+# Managed by the mesh (module memory-pressure). Replaced on every push; edit the catalogue instead.
+#
+# Swap-in reads one page, not eight: read-ahead exists to amortise a disk's seek, and compressed swap in
+# RAM has none — the speculation only costs decompression and memory.
+vm.page-cluster = 0
+#
+# vm.swappiness is deliberately left alone. The usual zram advice (150-180) holds only while the
+# compressed swap has room; once it is full, a higher swappiness moves pages to the disk swap, the thing
+# being avoided. Raise it only together with zram-size.

modules/memory-pressure/files/user-manager.conf

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+# Managed by the mesh (module memory-pressure). Replaced on every push; edit the catalogue instead.
+#
+# systemd-oomd may kill the worst unit in a person's service manager when its memory pressure stays
+# above 80 % — instead of the kernel freezing the machine.
+[Service]
+ManagedOOMMemoryPressure=kill
+ManagedOOMMemoryPressureLimit=80%

modules/memory-pressure/files/zram-generator.conf

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+# Managed by the mesh (module memory-pressure). Replaced on every push; edit the catalogue instead.
+#
+# Compressed swap in RAM: fast, at a higher priority than any swap on disk, so it takes the everyday
+# pressure before anything spills to a disk. Half the RAM, at most 16 GiB, compressed with zstd.
+# The swap on disk, its size and whether one exists at all are the machine's, not this module's.
+#
+# Read by the generator at boot: a change applies at the next boot.
+[zram0]
+zram-size = min(ram / 2, 16384)
+compression-algorithm = zstd
+swap-priority = 100