diff --git a/octoprint/printer.py b/octoprint/printer.py
index 442979c..bf2438b 100644
--- a/octoprint/printer.py
+++ b/octoprint/printer.py
@@ -29,6 +29,8 @@ def getConnectionOptions():
 
 class Printer():
 	def __init__(self, gcodeManager):
+		from collections import deque
+
 		self._gcodeManager = gcodeManager
 
 		# state
@@ -37,19 +39,19 @@ class Printer():
 		self._targetTemp = None
 		self._targetBedTemp = None
 		self._temps = {
-			"actual": [],
-			"target": [],
-			"actualBed": [],
-			"targetBed": []
+			"actual": deque([], 300),
+			"target": deque([], 300),
+			"actualBed": deque([], 300),
+			"targetBed": deque([], 300)
 		}
 		self._tempBacklog = []
 
 		self._latestMessage = None
-		self._messages = []
+		self._messages = deque([], 300)
 		self._messageBacklog = []
 
 		self._latestLog = None
-		self._log = []
+		self._log = deque([], 300)
 		self._logBacklog = []
 
 		self._state = None
@@ -233,12 +235,10 @@ class Printer():
 
 	def _addLog(self, log):
 		self._log.append(log)
-		self._log = self._log[-300:]
 		self._stateMonitor.addLog(log)
 
 	def _addMessage(self, message):
 		self._messages.append(message)
-		self._messages = self._messages[-300:]
 		self._stateMonitor.addMessage(message)
 
 	def _setProgressData(self, progress, filepos, printTime, printTimeLeft):
@@ -264,16 +264,9 @@ class Printer():
 		currentTimeUtc = int(time.time() * 1000)
 
 		self._temps["actual"].append((currentTimeUtc, temp))
-		self._temps["actual"] = self._temps["actual"][-300:]
-
 		self._temps["target"].append((currentTimeUtc, targetTemp))
-		self._temps["target"] = self._temps["target"][-300:]
-
 		self._temps["actualBed"].append((currentTimeUtc, bedTemp))
-		self._temps["actualBed"] = self._temps["actualBed"][-300:]
-
 		self._temps["targetBed"].append((currentTimeUtc, bedTargetTemp))
-		self._temps["targetBed"] = self._temps["targetBed"][-300:]
 
 		self._temp = temp
 		self._bedTemp = bedTemp
@@ -315,9 +308,9 @@ class Printer():
 		try:
 			data = self._stateMonitor.getCurrentData()
 			data.update({
-				"temperatureHistory": self._temps,
-				"logHistory": self._log,
-				"messageHistory": self._messages
+				"temperatureHistory": list(self._temps),
+				"logHistory": list(self._log),
+				"messageHistory": list(self._messages)
 			})
 			callback.sendHistoryData(data)
 		except Exception, err:
diff --git a/octoprint/util/comm.py b/octoprint/util/comm.py
index 1ce3fca..20d306e 100644
--- a/octoprint/util/comm.py
+++ b/octoprint/util/comm.py
@@ -366,6 +366,8 @@ class MachineCom(object):
 	STATE_TRANSFERING_FILE = 11
 	
 	def __init__(self, port = None, baudrate = None, callbackObject = None):
+		from collections import deque
+
 		self._logger = logging.getLogger(__name__)
 		self._serialLogger = logging.getLogger("SERIAL")
 
@@ -400,7 +402,7 @@ class MachineCom(object):
 		self._alwaysSendChecksum = settings().getBoolean(["feature", "alwaysSendChecksum"])
 		self._currentLine = 0
 		self._resendDelta = None
-		self._lastLines = []
+		self._lastLines = deque([], 50)
 
 		self._sendNextLock = threading.Lock()
 		self._sendingLock = threading.Lock()
@@ -971,15 +973,13 @@ class MachineCom(object):
 					self._currentLine = newLineNumber + 1
 
 					# after a reset of the line number we have no way to determine what line exactly the printer now wants
-					self._lastLines = []
+					self._lastLines.clear()
 					self._resendDelta = None
 					return
 			self._doSend(cmd, sendChecksum)
 
 	def _addToLastLines(self, cmd):
 		self._lastLines.append(cmd)
-		if len(self._lastLines) > 50:
-			self._lastLines = self._lastLines[-50:] # only keep the last 50 lines in memory
 		self._logger.debug("Got %d lines of history in memory" % len(self._lastLines))
 
 	def _doSend(self, cmd, sendChecksum=False):