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android_system_core/lmkd
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Mark Salyzyn 64d97d8761 lmkd: limit capability set to minimum 
Set F() capability set and 'drop' lmkd from AID_ROOT to AID_LMKD uid
and from AID_ROOT to AID_LMKD and AID_SYSTEM gid.

/dev/memcg/memory.pressure defaults to root.root mode 0000, set it up
as root.system mode 0040 to allow lmkd read access.

Instrument failure to set SCHED_FIFO.

Annotate access points that require elevated capabilities.

Test: check /proc/`pidof lmkd`/status for capability set
Test: lmkd_unit_test
Bug: 77650566
Change-Id: I986081a0434cf6e842b63a55726380205b30a3ea
 		2018-04-16 14:51:56 -07:00
..
include lmkd: Introduce liblmkd_utils for communicating with lmkd process 2018-03-09 11:18:53 -08:00
tests lmkd: test: access /sys/module/lowmemorykiller/ as u:r:shell:s0 2018-04-03 14:41:11 +00:00
Android.bp lmkd: only mlockall() if enabled 2018-04-03 14:41:26 +00:00
OWNERS
…
README.md lmkd: Introduce support for legacy kill algorithm that uses minfree levels 2018-04-15 16:02:36 +00:00
liblmkd_utils.c lmkd: Introduce liblmkd_utils for communicating with lmkd process 2018-03-09 11:18:53 -08:00
lmkd.c lmkd: limit capability set to minimum 2018-04-16 14:51:56 -07:00
lmkd.rc lmkd: limit capability set to minimum 2018-04-16 14:51:56 -07:00

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