Add a configuration to delay monitor initialization am: 1847e9d7ab

Original change: https://android-review.googlesource.com/c/platform/system/memory/lmkd/+/2650042

Change-Id: I6deffbc47fa0a6b7322cf35e41692a1ce0048c4c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

include/lmkd.h

@@ -36,6 +36,7 @@ enum lmk_cmd {
     LMK_PROCKILL,           /* Unsolicited msg to subscribed clients on proc kills */
     LMK_UPDATE_PROPS,       /* Reinit properties */
     LMK_STAT_KILL_OCCURRED, /* Unsolicited msg to subscribed clients on proc kills for statsd log */
+    LMK_START_MONITORING,   /* Start psi monitoring if it was skipped earlier */
 };
 
 /*
@@ -256,6 +257,15 @@ static inline size_t lmkd_pack_set_update_props(LMKD_CTRL_PACKET packet) {
     return sizeof(int);
 }
 
+/*
+ * Prepare LMK_START_MONITORING packet and return packet size in bytes.
+ * Warning: no checks performed, caller should ensure valid parameters.
+ */
+static inline size_t lmkd_pack_start_monitoring(LMKD_CTRL_PACKET packet) {
+    packet[0] = htonl(LMK_START_MONITORING);
+    return sizeof(int);
+}
+
 /*
  * Prepare LMK_UPDATE_PROPS reply packet and return packet size in bytes.
  * Warning: no checks performed, caller should ensure valid parameters.

lmkd.cpp

@@ -194,6 +194,7 @@ static int mpevfd[VMPRESS_LEVEL_COUNT] = { -1, -1, -1 };
 static bool pidfd_supported;
 static int last_kill_pid_or_fd = -1;
 static struct timespec last_kill_tm;
+static bool monitors_initialized;
 
 /* lmkd configurable parameters */
 static bool debug_process_killing;
@@ -216,6 +217,7 @@ static int64_t filecache_min_kb;
 static int64_t stall_limit_critical;
 static bool use_psi_monitors = false;
 static int kpoll_fd;
+static bool delay_monitors_until_boot;
 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 */
@@ -1510,7 +1512,7 @@ static void ctrl_command_handler(int dsock_idx) {
             goto wronglen;
         result = -1;
         if (update_props()) {
-            if (!use_inkernel_interface) {
+            if (!use_inkernel_interface && monitors_initialized) {
                 /* Reinitialize monitors to apply new settings */
                 destroy_monitors();
                 if (init_monitors()) {
@@ -1533,6 +1535,24 @@ static void ctrl_command_handler(int dsock_idx) {
             exit(1);
         }
         break;
+    case LMK_START_MONITORING:
+        if (nargs != 0)
+            goto wronglen;
+        // Registration is needed only if it was skipped earlier.
+        if (monitors_initialized)
+            return;
+        if (!property_get_bool("sys.boot_completed", false)) {
+            ALOGE("LMK_START_MONITORING cannot be handled before boot completed");
+            return;
+        }
+
+        if (!init_monitors()) {
+            /* Failure to start psi monitoring, crash to be restarted */
+            ALOGE("Failure to initialize monitoring. Exiting...");
+            exit(1);
+        }
+        ALOGI("Initialized monitors after boot completed.");
+        break;
     default:
         ALOGE("Received unknown command code %d", cmd);
         return;
@@ -3343,6 +3363,7 @@ static bool init_monitors() {
     } else {
         ALOGI("Using vmpressure for memory pressure detection");
     }
+    monitors_initialized = true;
     return true;
 }
 
@@ -3482,8 +3503,13 @@ static int init(void) {
             }
         }
     } else {
-        if (!init_monitors()) {
+        // Do not register monitors until boot completed for devices configured
-            return -1;
+        // for delaying monitors. This is done to save CPU cycles for low
+        // resource devices during boot up.
+        if (!delay_monitors_until_boot || property_get_bool("sys.boot_completed", false)) {
+            if (!init_monitors()) {
+                return -1;
+            }
         }
         /* let the others know it does support reporting kills */
         property_set("sys.lmk.reportkills", "1");
@@ -3749,6 +3775,7 @@ static bool update_props() {
     swap_util_max = clamp(0, 100, GET_LMK_PROPERTY(int32, "swap_util_max", 100));
     filecache_min_kb = GET_LMK_PROPERTY(int64, "filecache_min_kb", 0);
     stall_limit_critical = GET_LMK_PROPERTY(int64, "stall_limit_critical", 100);
+    delay_monitors_until_boot = GET_LMK_PROPERTY(bool, "delay_monitors_until_boot", false);
 
     reaper.enable_debug(debug_process_killing);