defaults: Configure multi-gen LRU thrashing prevention

See https://www.kernel.org/doc/html/next/admin-guide/mm/multigen_lru.html

> Based on the average human detectable lag (~100ms), N=1000 usually eliminates
> intolerable janks due to thrashing. Larger values like N=3000 make janks less
> noticeable at the risk of premature OOM kills.

debian/librem5-base-defaults.librem5-mglru.service

+[Unit]
+Description=Configure multi-gen LRU thrashing prevention
+Documentation=https://www.kernel.org/doc/html/next/admin-guide/mm/multigen_lru.html
+ConditionPathExists=/sys/kernel/mm/lru_gen/min_ttl_ms
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/bin/sh -c 'echo 1000 > /sys/kernel/mm/lru_gen/min_ttl_ms'
+ExecStop=/bin/sh -c 'echo 0 > /sys/kernel/mm/lru_gen/min_ttl_ms'
+
+[Install]
+WantedBy=basic.target

debian/rules

@@ -18,6 +18,7 @@ override_dh_installsystemd:
 	dh_installsystemd --no-start --name=usb_gadget
 	dh_installsystemd --no-start --name=bluetooth-brcmfmac
 	dh_installsystemd --no-start --name=librem5-lockdown-support
+	dh_installsystemd --no-start --name=librem5-mglru
 
 override_dh_installsystemduser:
 	dh_installsystemduser --name=mpris-proxy