lmkd: Do not re-initialize lmkd when persistent properties are loaded

When a device boots, lmkd starts before persistent properties are loaded,
therefore if experiments set any flags, the corresponding persistent
properties will trigger change notifications when they are first loaded
during boot.
In order to prevent lmkd from re-initializing on every property load,
mark persistent property change by setting lmkd.reinit to 0 and delay
lmkd re-initialization until sys.boot_completed=1 when all properties
are set and only one re-initialization will capture them all. On devices
with no experiment flags being set lmkd.reinit will be undefined at the
boot completion time and re-initialization will not be triggered at all.

Bug: 194316048
Test: adb shell device_config put lmkd_native thrashing_limit_critical 350
Test: adb shell device_config put lmkd_native thrashing_limit 100
Test: adb reboot; adb -b all logcat | grep lmkd
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: Iba34fc719a18d58b890549c7415bec869d471901
Merged-In: Iba34fc719a18d58b890549c7415bec869d471901
(cherry picked from commit aced711991ac2ab8c6d0d104127358dcdcc9886b)
2 files changed
tree: 5722c59c12ed5455accbe51be2ce4f05d8f99e74
  1. include/
  2. libpsi/
  3. tests/
  4. Android.bp
  5. event.logtags
  6. liblmkd_utils.cpp
  7. lmkd.cpp
  8. lmkd.rc
  10. README.md
  11. statslog.cpp
  12. statslog.h

Android Low Memory Killer Daemon


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.

Android Properties

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

ro.lmk.swap_free_low_percentage: level of free swap as a percentage of the total swap space used as a threshold to consider the system as swap space starved. Default for low-RAM devices = 10, for high-end devices = 20

ro.lmk.thrashing_limit: number of workingset refaults as a percentage of the file-backed pagecache size used as a threshold to consider system thrashing its pagecache. Default for low-RAM devices = 30, for high-end devices = 100

ro.lmk.thrashing_limit_decay: thrashing threshold decay expressed as a percentage of the original threshold used to lower the threshold when system does not recover even after a kill. Default for low-RAM devices = 50, for high-end devices = 10

ro.lmk.psi_partial_stall_ms: partial PSI stall threshold in milliseconds for triggering low memory notification. Default for low-RAM devices = 200, for high-end devices = 70

ro.lmk.psi_complete_stall_ms: complete PSI stall threshold in milliseconds for triggering critical memory notification. Default = 700

lmkd will set the following Android properties according to current system configurations:

sys.lmk.minfree_levels: minfree:oom_adj_score pairs, delimited by comma

sys.lmk.reportkills: whether or not it supports reporting process kills to clients. Test app should check this property before testing low memory kill notification. Default will be unset.