Add unitary test for memory profiling

Makefile

@@ -74,6 +74,18 @@ trace-malloc: ## Trace the malloc() calls
 memory-leak: ## Profile memory leaks
 	./venv/bin/python -m glances -C ./conf/glances.conf --memory-leak
 
+memory-profiling: ## Profile memory usage
+	@echo "It's a very long test (~4 hours)..."
+	rm -f mprofile_*.dat
+	@echo "1/2 - Start memory profiling with the history option enable"
+	./venv/bin/mprof run -T 1 -C run.py -C ./conf/glances.conf --stop-after 2400 --quiet
+	./venv/bin/mprof plot --output ./docs/_static/glances-memory-profiling-with-history.png
+	rm -f mprofile_*.dat
+	@echo "2/2 - Start memory profiling with the history option disable"
+	./venv/bin/mprof run -T 1 -C run.py -C ./conf/glances.conf --disable-history --stop-after 2400 --quiet
+	./venv/bin/mprof plot --output ./docs/_static/glances-memory-profiling-without-history.png
+	rm -f mprofile_*.dat
+
 # ===================================================================
 # Docs
 # ===================================================================

conf/glances.conf

@@ -10,8 +10,8 @@ refresh=2
 # Does Glances should check if a newer version is available on PyPI ?
 check_update=true
 # History size (maximum number of values)
-# Default is 3600 seconds (1 hour)
-history_size=3600
+# Default is 1200 values (~1h with the default refresh rate)
+history_size=1200
 
 ##############################################################################
 # User interface

dev-requirements.txt

@@ -6,3 +6,5 @@ flake8
 autopep8
 autoflake
 codespell
+memory-profiler
+matplotlib

glances/plugins/glances_plugin.py

@@ -178,13 +178,13 @@ class GlancesPlugin(object):
 
     def update_stats_history(self):
         """Update stats history."""
+        # Build the history
+        if self.get_export() and self.history_enable():
             # If the plugin data is a dict, the dict's key should be used
             if self.get_key() is None:
                 item_name = ''
             else:
                 item_name = self.get_key()
-        # Build the history
-        if self.get_export() and self.history_enable():
             for i in self.get_items_history_list():
                 if isinstance(self.get_export(), list):
                     # Stats is a list of data