metrics.py: add free RAM figure.

Author: peterhinch

v3/as_drivers/metrics/metrics.py

@@ -1,4 +1,9 @@
+# metrics.py Check on scheduling performance of an application
+# Released under the MIT licence
+# Copyright (c) Peter Hinch 2020
+
 import uasyncio as asyncio
+import gc
 from utime import ticks_us, ticks_diff
 
 
@@ -23,15 +28,18 @@ async def func():
                 ncalls += 1
                 t_last = t
             print(st.format(max_d, min_d, tot_d//ncalls, ncalls, ncalls//10))
+            gc.collect()
+            print('mem free', gc.mem_free())
             ncalls = 0
             max_d = 0
             min_d = 100_000_000
             tot_d = 0
     return func
 
+# Example of call
 async def main():
-    asyncio.create_task(metrics()())
+    asyncio.create_task(metrics()())  # Note the syntax
     while True:
         await asyncio.sleep(0)
 
-asyncio.run(main())
+#asyncio.run(main())