Merge "lmkd: introduce lowmem_min_oom_score tunable" into main

README.md

@@ -100,6 +100,12 @@ properties:
                                  to 0 will ignore available memory and assume that
                                  configured swap size can be always utilized fully.
                                  Default = 1 (no compression).
+  - `ro.lmk.lowmem_min_oom_score`: min oom_score_adj level used to select processes
+                                 to kill when memory is critically low. Setting it
+                                 to 1001 will prevent any kills for this reason. Min
+                                 acceptable value is 201 (apps up to perceptible).
+                                 Default = 701 (all cached apps excluding the last
+                                 active one).
 
 lmkd will set the following Android properties according to current system
 configurations:

lmkd.cpp

@@ -164,6 +164,8 @@ static inline void trace_kill_end() {}
 #define DEF_DIRECT_RECL_THRESH_MS 0
 /* ro.lmk.swap_compression_ratio property defaults */
 #define DEF_SWAP_COMP_RATIO 1
+/* ro.lmk.lowmem_min_oom_score defaults */
+#define DEF_LOWMEM_MIN_SCORE (PREVIOUS_APP_ADJ + 1)
 
 #define LMKD_REINIT_PROP "lmkd.reinit"
 
@@ -235,6 +237,7 @@ static int kpoll_fd;
 static bool delay_monitors_until_boot;
 static int direct_reclaim_threshold_ms;
 static int swap_compression_ratio;
+static int lowmem_min_oom_score;
 static struct psi_threshold psi_thresholds[VMPRESS_LEVEL_COUNT] = {
     { PSI_SOME, 70 },    /* 70ms out of 1sec for partial stall */
     { PSI_SOME, 100 },   /* 100ms out of 1sec for partial stall */
@@ -2932,7 +2935,7 @@ update_watermarks:
         kill_reason = LOW_MEM;
         snprintf(kill_desc, sizeof(kill_desc), "%s watermark is breached",
             wmark < WMARK_LOW ? "min" : "low");
-        min_score_adj = PREVIOUS_APP_ADJ + 1;
+        min_score_adj = lowmem_min_oom_score;
     }
 
     /* Kill a process if necessary */
@@ -4016,6 +4019,9 @@ static bool update_props() {
             GET_LMK_PROPERTY(int64, "direct_reclaim_threshold_ms", DEF_DIRECT_RECL_THRESH_MS);
     swap_compression_ratio =
             GET_LMK_PROPERTY(int64, "swap_compression_ratio", DEF_SWAP_COMP_RATIO);
+    lowmem_min_oom_score =
+            std::max(PERCEPTIBLE_APP_ADJ + 1,
+                     GET_LMK_PROPERTY(int32, "lowmem_min_oom_score", DEF_LOWMEM_MIN_SCORE));
 
     reaper.enable_debug(debug_process_killing);
 

lmkd.rc

@@ -58,3 +58,6 @@ on property:persist.device_config.lmkd_native.direct_reclaim_threshold_ms=*
 
 on property:persist.device_config.lmkd_native.swap_compression_ratio=*
     setprop lmkd.reinit ${sys.boot_completed:-0}
+
+on property:persist.device_config.lmkd_native.lowmem_min_oom_score=*
+    setprop lmkd.reinit ${sys.boot_completed:-0}