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Only thread group leaders should be registered with lmkd. Add a check to ignore any non-leader TIDs and generate an error if such condition is detected. Run the same check before killing a process to detect cases of non-leader TIDs being used to kill a process. This might happen if PIDs overflow and previously registered PID gets reused for a non-leader thread in the following scenario: 1. pid X is a thread group leader and is registered with lmkd 2. pid X dies without lmkd knowing it and pid gets recycled 3. process Y creates a thread with tid X 4. lmkd kills pid X which results in process Y being killed Bug: 136408020 Test: lmkd_unit_test Change-Id: I46c5a0b273f2b72cefc20ec59b80b4393f2a1a37 Signed-off-by: Suren Baghdasaryan <surenb@google.com> |
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| .. | ||
| include | ||
| libpsi | ||
| tests | ||
| Android.bp | ||
| event.logtags | ||
| liblmkd_utils.c | ||
| lmkd.c | ||
| lmkd.rc | ||
| OWNERS | ||
| README.md | ||
| statslog.c | ||
| statslog.h | ||
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