Add non PID specific total memory metric. (#230)

* Add non PID specific total memory metric.

* Add non PID specific memory utilization metric.

Author: umaannamalai

newrelic/samplers/memory_usage.py

@@ -25,7 +25,16 @@
 PID = os.getpid()
 
 
-@data_source_generator(name='Memory Usage')
+@data_source_generator(name="Memory Usage")
 def memory_usage_data_source():
-    yield ('Memory/Physical/%d' % (PID), physical_memory_used())
-    yield ('Memory/Physical/Utilization/%d' % (PID), physical_memory_used()/total_physical_memory())
+    yield ("Memory/Physical", physical_memory_used())
+    yield ("Memory/Physical/%d" % (PID), physical_memory_used())
+
+    yield (
+        "Memory/Physical/Utilization",
+        physical_memory_used() / total_physical_memory(),
+    )
+    yield (
+        "Memory/Physical/Utilization/%d" % (PID),
+        physical_memory_used() / total_physical_memory(),
+    )

tests/agent_unittests/test_sampler_metrics.py

@@ -151,7 +151,9 @@ def test_cpu_metrics_collection(cpu_data_source):
 
 
 EXPECTED_MEMORY_METRICS = (
+    "Memory/Physical",
     "Memory/Physical/%d" % PID,
+    "Memory/Physical/Utilization",
     "Memory/Physical/Utilization/%d" % PID,
 )