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Suren Baghdasaryan 7c3addb2a1 lmkd: Use process_mrelease to reap the target process from a thread process_mrelease syscall can be used to expedite memory release of a process after it was killed. This allows memory to be released without the target process being scheduled, therefore does not depend on target's priority or the CPU it's running on. However process_mrelease syscall can take considerable time. Blocking lmkd main thread during that time can cause memory pressure events being missed while lmkd is busy reaping previous target's memory. For this reason reaping should be done in a separate thread. This way lmkd main thread can keep monitoring memory pressure while memory is being released. Introduce Reaper class which maintains a pool of threads to perform process killing and reaping. The main thread submits a request to the Reaper to kill and reap the process without blocking. If all the threads in the pool are busy at the time the next kill is needed, the kill is performed by the main thread without reaping. Bug: 130172058 Bug: 189803002 Signed-off-by: Suren Baghdasaryan <surenb@google.com> Change-Id: If7b10fdd1838bdfeea3fed3031565feffe0b52be		2022-01-06 18:14:14 +00:00
include	lmkd: reroute atoms logging to AMS	2021-05-11 00:00:56 +00:00
libpsi	[LSC] Add LOCAL_LICENSE_KINDS to system/memory/lmkd	2021-02-12 18:10:32 -08:00
tests	[LSC] Add LOCAL_LICENSE_KINDS to system/memory/lmkd	2021-02-12 18:10:32 -08:00
.clang-format	lmkd: Add clang format symlink	2020-11-24 13:09:01 -05:00
Android.bp	lmkd: Use process_mrelease to reap the target process from a thread	2022-01-06 18:14:14 +00:00
OWNERS	Add lmkd/OWNERS.	2017-12-08 16:12:58 -08:00
README.md	lmkd: Support to send unsolicited message to clients	2019-12-12 08:53:04 -08:00
event.logtags	lmkd: Add thrashing and max_thrashing into killinfo reports	2021-08-09 15:10:46 -07:00
liblmkd_utils.cpp	lmkd: Remove unused variables and fix type mismatches	2020-05-11 19:52:52 -07:00
lmkd.cpp	lmkd: Use process_mrelease to reap the target process from a thread	2022-01-06 18:14:14 +00:00
lmkd.rc	Replace writepid with task_profiles command for cgroup migration	2021-10-15 16:40:18 +00:00
reaper.cpp	lmkd: Use process_mrelease to reap the target process from a thread	2022-01-06 18:14:14 +00:00
reaper.h	lmkd: Use process_mrelease to reap the target process from a thread	2022-01-06 18:14:14 +00:00
statslog.cpp	lmkd: Add current and max thrashing levels in LMK_MEMORY_STATS reports	2021-07-23 19:11:36 +00:00
statslog.h	lmkd: Add current and max thrashing levels in LMK_MEMORY_STATS reports	2021-07-23 19:11:36 +00:00

README.md

Android Low Memory Killer Daemon

Introduction

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.

Background

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.