serial heap status messages (#11340)

src/Power.cpp

@@ -86,6 +86,12 @@
 #define DELAY_FOREVER portMAX_DELAY
 #endif
 
+// How often the free-heap line is written to the debug log. The Power thread polls every
+// 20s once it is initialized, so that is the effective granularity. Set to 0 to disable.
+#ifndef HEAP_LOG_INTERVAL_MS
+#define HEAP_LOG_INTERVAL_MS (5 * 60 * 1000)
+#endif
+
 #if defined(BATTERY_PIN) && defined(ARCH_ESP32)
 
 #ifndef BAT_MEASURE_ADC_UNIT // ADC1 is default
@@ -1075,9 +1081,42 @@ void Power::readPowerStatus()
     }
 }
 
+/**
+ * Emit a free-heap line to the debug log every HEAP_LOG_INTERVAL_MS, so a slow leak shows up
+ * as a trend in a field log instead of only as an out-of-memory reboot. Unlike the DEBUG_HEAP
+ * instrumentation above this is always on, and costs one line per interval.
+ */
+void Power::logHeapUsage()
+{
+#if HEAP_LOG_INTERVAL_MS > 0
+    if (Throttle::isWithinTimespanMs(lastHeapLogTime, HEAP_LOG_INTERVAL_MS))
+        return;
+
+    const uint32_t heapTotal = memGet.getHeapSize();
+    // Platforms without heap accounting report UINT32_MAX (or 0) - nothing worth logging
+    if (heapTotal == 0 || heapTotal == UINT32_MAX)
+        return;
+
+    const uint32_t heapFree = memGet.getFreeHeap();
+    // The first line has no earlier sample to difference against
+    const int32_t delta = lastHeapLogTime ? (int32_t)(heapFree - lastHeapLogFree) : 0;
+
+    const uint32_t psramTotal = memGet.getPsramSize();
+    if (psramTotal)
+        LOG_INFO("Heap: %u/%u bytes free (%d since last), PSRAM: %u/%u bytes free", heapFree, heapTotal, delta,
+                 memGet.getFreePsram(), psramTotal);
+    else
+        LOG_INFO("Heap: %u/%u bytes free (%d since last)", heapFree, heapTotal, delta);
+
+    lastHeapLogFree = heapFree;
+    lastHeapLogTime = millis();
+#endif
+}
+
 int32_t Power::runOnce()
 {
     readPowerStatus();
+    logHeapUsage();
 
 #ifdef HAS_PMU
     // WE no longer use the IRQ line to wake the CPU (due to false wakes from

src/Power.h

@@ -93,6 +93,7 @@ class Power : public concurrency::OSThread
 
     void powerCommandsCheck();
     void readPowerStatus();
+    void logHeapUsage();
     virtual bool setup();
     virtual int32_t runOnce() override;
     void setStatusHandler(meshtastic::PowerStatus *handler) { statusHandler = handler; }
@@ -131,6 +132,9 @@ class Power : public concurrency::OSThread
     // open circuit voltage lookup table
     uint8_t low_voltage_counter;
     uint32_t lastLogTime = 0;
+    // Periodic free-heap logging: time of the last line emitted, and the reading it carried
+    uint32_t lastHeapLogTime = 0;
+    uint32_t lastHeapLogFree = 0;
 
 #ifdef ARCH_ESP32
     // Get notified when lightsleep begins and ends