ports/esp32/main.c: Limit uPy heap size to a ratio of IDF heap size.

tom-van · tom-van · commit 07c1ef8117fb · 2021-12-16T01:04:06.000+01:00
Before this change the largest free heap block was allocated for uPy heap.
ESP32 S2 and S3 has different memory layout and this method results
in so small remaining IDF heap that WiFi and other tasks breaks.

The heuristic ratio was chosen as an usable compromise betwen
uPy and IDF heap sizes for devices using WiFi and TLS
and fine tuned to preserve original uPy heap size on ESP32 and IDF 4.0.

Allocation on SPIRAM-equipped devices is not changed.

Signed-off-by: Tomas Vanek &lt;vanekt@fbl.cz&gt;
diff --git a/ports/esp32/main.c b/ports/esp32/main.c
@@ -127,9 +127,18 @@ void mp_task(void *pvParameter) {
     #endif
 
     // If we have no SPIRAM,
-    // allocate the uPy heap using malloc and get the largest available region
+    // allocate the uPy heap using malloc
     if (!mp_task_heap_size) {
-        mp_task_heap_size = heap_caps_get_largest_free_block(MALLOC_CAP_8BIT);
+        size_t largest_free = heap_caps_get_largest_free_block(MALLOC_CAP_8BIT);
+
+        // IDF 4.0 does not provide heap_caps_get_total_size(), use
+        // total free instead as there is little memory allocated now
+        size_t total_free = heap_caps_get_free_size(MALLOC_CAP_8BIT);
+
+        // Use a heuristic ratio to split uPy heap and the remaining IFD heap
+        // or use the largest available region if smaller
+        // Fine tuned to leave uPy heap 111168 bytes on ESP32 and IDF 4.0.2
+        mp_task_heap_size = MIN(largest_free, total_free * 7 / 8 - 68249);
         mp_task_heap = malloc(mp_task_heap_size);
     }
 
