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Suren Baghdasaryan b2d59ee367 lmkd: Optimize frequent file reads by keeping file descriptors open 
To check system memory state lmkd is using same files every time vmpressure
event is received. Instead of opening and closing these files every time
we store the file descriptor and use pread() to reread the file from
the beginning.

Bug: 77299493
Bug: 75322373
Change-Id: I8e27f8b9526e82e3cc313a02fce215c2e4dd3d29
Merged-In: I8e27f8b9526e82e3cc313a02fce215c2e4dd3d29
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
(cherry picked from commit d716fe3610)
2018-04-16 09:33:44 -07:00
..
include lmkd: Introduce liblmkd_utils for communicating with lmkd process 2018-01-31 18:10:49 +00:00
tests lmkd: Implement lmkd-test 2018-01-31 18:11:38 +00:00
Android.bp Use usel_mkd_stats_log build variable while compiling lmkd with stats logging feature. 2018-03-23 20:33:57 +00:00
liblmkd_utils.c lmkd: Introduce liblmkd_utils for communicating with lmkd process 2018-01-31 18:10:49 +00:00
lmkd.c lmkd: Optimize frequent file reads by keeping file descriptors open 2018-04-16 09:33:44 -07:00
lmkd.rc Enable hidepid=2 on /proc 2015-11-09 09:08:46 -08:00
OWNERS Add lmkd/OWNERS. 2017-12-08 16:12:58 -08:00
README.md lmkd: Add lmkd README file 2018-04-16 09:26:40 -07:00
statslog.c Functions to log stats log from LMKD. 2018-01-29 15:18:04 -08:00
statslog.h Fix compilation issue when LMKD_LOG_STATS is defined. 2018-03-26 18:15:25 +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.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