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platform_system_core/lmkd/README.md
Suren Baghdasaryan c09b53db7b lmkd: Introduce support for legacy kill algorithm that uses minfree levels 
Add ability to switch to the algorithm used by lowmemorykiller driver
for determining when to kill. It uses minfree levels to decide at which
levels of free memory and file cache to kill a process. oom_adj_score
is also determined by comparing current memory resources against minfree
levels.
ro.lmk.use_minfree_levels property is introduces for switching into this
mode. By default it is disabled.

Bug: 77299493
Bug: 75322373
Merged-In: I6b51972951026854a079fcda33d6786b7ed035e4
Change-Id: I6b51972951026854a079fcda33d6786b7ed035e4
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
2018-04-15 16:02:36 +00:00

2.6 KiB
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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