101 lines
4.4 KiB
Markdown
101 lines
4.4 KiB
Markdown
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Android Low Memory Killer Daemon
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================================
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Introduction
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------------
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Android Low Memory Killer Daemon (lmkd) is a process monitoring memory
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state of a running Android system and reacting to high memory pressure
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by killing the least essential process(es) to keep system performing
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at acceptable levels.
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Background
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----------
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Historically on Android systems memory monitoring and killing of
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non-essential processes was handled by a kernel lowmemorykiller driver.
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Since Linux Kernel 4.12 the lowmemorykiller driver has been removed and
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instead userspace lmkd daemon performs these tasks.
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Android Properties
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------------------
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lmkd can be configured on a particular system using the following Android
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properties:
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ro.config.low_ram: choose between low-memory vs high-performance
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device. Default = false.
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ro.lmk.use_minfree_levels: use free memory and file cache thresholds for
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making decisions when to kill. This mode works
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the same way kernel lowmemorykiller driver used
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to work. Default = false
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ro.lmk.low: min oom_adj score for processes eligible to be
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killed at low vmpressure level. Default = 1001
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(disabled)
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ro.lmk.medium: min oom_adj score for processes eligible to be
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killed at medium vmpressure level. Default = 800
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(non-essential processes)
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ro.lmk.critical: min oom_adj score for processes eligible to be
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killed at critical vmpressure level. Default = 0
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(all processes)
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ro.lmk.critical_upgrade: enables upgrade to critical level. Default = false
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ro.lmk.upgrade_pressure: max mem_pressure at which level will be upgraded
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because system is swapping too much. Default = 100
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(disabled)
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ro.lmk.downgrade_pressure: min mem_pressure at which vmpressure event will
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be ignored because enough free memory is still
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available. Default = 100 (disabled)
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ro.lmk.kill_heaviest_task: kill heaviest eligible task (best decision) vs.
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any eligible task (fast decision). Default = false
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ro.lmk.kill_timeout_ms: duration in ms after a kill when no additional
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kill will be done. Default = 0 (disabled)
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ro.lmk.debug: enable lmkd debug logs, Default = false
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ro.lmk.swap_free_low_percentage: level of free swap as a percentage of the
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total swap space used as a threshold to consider
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the system as swap space starved. Default for
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low-RAM devices = 10, for high-end devices = 20
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ro.lmk.thrashing_limit: number of workingset refaults as a percentage of
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the file-backed pagecache size used as a threshold
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to consider system thrashing its pagecache.
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Default for low-RAM devices = 30, for high-end
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devices = 100
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ro.lmk.thrashing_limit_decay: thrashing threshold decay expressed as a
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percentage of the original threshold used to lower
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the threshold when system does not recover even
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after a kill. Default for low-RAM devices = 50,
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for high-end devices = 10
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ro.lmk.psi_partial_stall_ms: partial PSI stall threshold in milliseconds for
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triggering low memory notification. Default for
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low-RAM devices = 200, for high-end devices = 70
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ro.lmk.psi_complete_stall_ms: complete PSI stall threshold in milliseconds for
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triggering critical memory notification. Default =
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700
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lmkd will set the following Android properties according to current system
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configurations:
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sys.lmk.minfree_levels: minfree:oom_adj_score pairs, delimited by comma
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sys.lmk.reportkills: whether or not it supports reporting process kills
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to clients. Test app should check this property
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before testing low memory kill notification.
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Default will be unset.
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