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Commit 7e5dea82 authored by Suren Baghdasaryan's avatar Suren Baghdasaryan
Browse files

lmkd: Add lmkd README file 



Add README file providing lmkd overview and description for its
properties.

Change-Id: I30236dd4ccaa2b48c31dfb80b63f0b82b49b5744
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
parent cd71fd51

lmkd/README.md

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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.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