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Martin Liu 1f72f5fa4b lmkd: adjust thrashing dection strategy When a device is thrashing the file cache, workingset refaults can grow slowly because of variant reasons. Current thrashing detection mechanism could reset the thrashing counter frequently as it relies on presence of reclaim activity, however refaults can keep increasing even when the device is not actively reclaiming. In addition, the thrashing counter gets reset when conditions require a kill but lmkd could not find an eligible process to be killed. This is problematic because when this happens thrashing is being ignored. Use a fixed 1 sec periods to aggregate the thrashing counter. Also we need to keep monitoring thrashing counter while retrying as someone could release the memory to mitigate the thrashing. If thrashing counter is greater than the limit at the end of the 1 sec period this means lmkd failed to find an eligible process to kill. In this case we store accumulated thrashing in case a new eligible process appears until accumulated thrashing is less that the limit or we miss an entire 1 sec window. Bug: 163134367 Test: heavy loading launch Signed-off-by: Martin Liu <liumartin@google.com> Change-Id: Ie9f4121ea604179c0ad510cc8430e7a6aec6e6b2		2020-08-28 13:04:42 +08:00
include	lmkd: Add property re-initialization support	2020-05-06 15:05:04 -07:00
libpsi	Include what you use: <stdio.h> and <unistd.h>	2020-04-13 15:21:09 -07:00
tests	lmkd_test: set process types	2020-03-09 13:17:51 +08:00
Android.bp	lmkd: Enable stricter compiler checks	2020-05-12 02:56:41 +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 lmkd wakeup information into killinfo logs	2020-07-24 19:31:03 +00:00
liblmkd_utils.cpp	lmkd: Remove unused variables and fix type mismatches	2020-05-11 19:52:52 -07:00
lmkd.cpp	lmkd: adjust thrashing dection strategy	2020-08-28 13:04:42 +08:00
lmkd.rc	lmkd: Add property re-initialization support	2020-05-06 15:05:04 -07:00
statslog.cpp	Emit swap size in the killed process' statsd atoms	2020-08-12 20:24:56 +01:00
statslog.h	Emit swap size in the killed process' statsd atoms	2020-08-12 20:24:56 +01:00

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.