Android Low Memory Killer Daemon (lmkd) is a process monitoring memory
state of a running Android system and reacting to high memory pressure
by killing the least essential process(es) to keep system performing
at acceptable levels.
Historically on Android systems memory monitoring and killing of
non-essential processes was handled by a kernel lowmemorykiller driver.
Since Linux Kernel 4.12 the lowmemorykiller driver has been removed and
instead userspace lmkd daemon performs these tasks.
lmkd can be configured on a particular system using the following Android
properties:
ro.config.low_ram: choose between low-memory vs high-performance
device. Default = false.
ro.lmk.use_minfree_levels: use free memory and file cache thresholds for
making decisions when to kill. This mode works
the same way kernel lowmemorykiller driver used
to work. Default = false
ro.lmk.low: min oom_adj score for processes eligible to be
killed at low vmpressure level. Default = 1001
(disabled)
ro.lmk.medium: min oom_adj score for processes eligible to be
killed at medium vmpressure level. Default = 800
(non-essential processes)
ro.lmk.critical: min oom_adj score for processes eligible to be
killed at critical vmpressure level. Default = 0
(all processes)
ro.lmk.critical_upgrade: enables upgrade to critical level. Default = false
ro.lmk.upgrade_pressure: max mem_pressure at which level will be upgraded
because system is swapping too much. Default = 100
(disabled)
ro.lmk.downgrade_pressure: min mem_pressure at which vmpressure event will
be ignored because enough free memory is still
available. Default = 100 (disabled)
ro.lmk.kill_heaviest_task: kill heaviest eligible task (best decision) vs.
any eligible task (fast decision). Default = false
ro.lmk.kill_timeout_ms: duration in ms after a kill when no additional
kill will be done, Default = 0 (disabled)
ro.lmk.debug: enable lmkd debug logs, Default = false
