System Introspection for System Analysis on Mobile Devices

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their system clocks with a network time protocol 1 daemon running on the samelaptop the probe is installed on.7.2 Measuring the Different LatenciesTo make a decision <strong>for</strong> next steps based on the data exchanged between theprobe and the client the time between sending and receiving data must bereduced to a minimum. The time delay between sending and receiving iscalled latency.7.2.1 GoalSending data over a network implies several components in the chain of <strong>for</strong>wardingdata (e.g. sending a message over a communication server to a recipient)Each component consumes time <strong>for</strong> processing and <strong>for</strong>warding the datawhich makes it obvious that a latency exists <strong>for</strong> exchanging data between theprobe and the client. Due to the fact that the components of the robot offerdifferent in<strong>for</strong>mation values with different frequencies, its important to reducethe latency. The goal of the first evaluation was to measure this latency regardingdifferent payloads and frequencies when exchanging data. Is the latencyhigher if a bigger payload is exchanged? Does a higher frequency increase thelatency or could it be constant <strong>for</strong> smaller payloads? The following methodwill try to give an answer on those questions.7.2.2 PreparationsFor the test an evaluation component thread was created on the probe. Thiscomponent thread was designed to send messages by configuring several parametersconcerning the frequency and the payload. For each test one out ofthree patterns can be selected which gets automatically added to each message.Table 7.1 shows the patterns predefined. Also the delay between two messagescan be set which is used to simulate a frequency <strong>for</strong> exchanging data. Settingthis delay to zero will result in a maximum possible frequency due to sendinga message in every step. For the configuration of each test a simple GUI iscreated and each test can be executed from within this GUI. On the client sidea corresponding component view <strong>for</strong> receiving the messages is created. Thecomponent view is capable of storing data by writing data to a logging file onthe clients file system.1 http://www.webcitation.org/5xCmxgeBb - The Network Time Protocol (NTP)55
Name Description CharactersSingleline attached is one value pair to the properties.135The used key is “LINE1” and theproperty contains 100 charactersMultiline attached are 10 value pairs to the properties.1035The used keys are “LINE1” to“LINE10”. Each property contains 100charactersComplex Data attached to this message is the output ofthe SLAM sensor containing the image ofthe slam map translated to an image andthree value pairs containing date about thenumber of the image and the position ofthe robot5000Table 7.1: Patterns used <strong>for</strong> the first part of evaluation - The characterscolumn shows the total count of characters of theproperties attached to a single message.7.2.3 MethodA test series with a total of 18 tests was per<strong>for</strong>med. For each test the probe<strong>for</strong>wards a total of 200 messages to the connected client. For the first ninetests the mobile device was connected as client to the probe. For the secondnine tests the client connected was the separate laptop. For a single test theevaluation component on the probe was configured with the parameters shownin Table 7.2. Parameters were the amount of messages send to the client, thedelay between two messages and the pattern attached to each message. Whena single test was executed, the probe first sends a message containing the nameof the logging file. The client creates the file according to the given name onits local file system. Once the component thread has send the name of thelogging file the messages <strong>for</strong> the test are <strong>for</strong>warded according the parametersconfigured in the GUI. Whenever a message arrives on the client side, the clientstores its current timestamp to a variable. From the received message the timeof the probe gets parsed and stored to a variable. Due to the fact that thereceived data normally is processed somehow, work on the data is simulatedby iterating of the properties of each message and counting its characters. Atthe end of simulating work the stored variables are appended to the loggingfile. When the component thread reaches the configured amount of messageto be send it automatically stops and the test ends.56
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Bringing System <s
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AbstractSystem <st
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output, so each component is offeri
Page 9 and 10: of the system and the decisions mad
Page 11 and 12: created a telelaboratory where two
Page 13 and 14: Like the telelaboratory there is a
Page 15 and 16: with a very high frequency which ma
Page 17 and 18: Due to improving technology the use
Page 19 and 20: Figure 4.1: ToBI platfor</s
Page 21 and 22: Figure 4.3: The architecture behind
Page 23 and 24: Figure 4.5: Typical instant messagi
Page 25 and 26: 5 System DesignThe
Page 27 and 28: Figure 5.2: Message exchange betwee
Page 29 and 30: Figure 5.4: Beacon running between
Page 31 and 32: Figure 5.5: Reading and processing
Page 33 and 34: data and only forw
Page 35 and 36: For example a developer can select
Page 37 and 38: Figure 5.13: Principle of tabbed na
Page 39 and 40: 6.1 The Communication InterfaceThe
Page 41 and 42: 6.2 The Probe - Implementation of t
Page 43 and 44: stop all active processes of the co
Page 45 and 46: is received containing the TAG of t
Page 47 and 48: The selected sensors give a good im
Page 49 and 50: 1 2 4 6 8 Listing 6.2: Example of t
Page 51 and 52: TabConfig - The Status ViewThe TabC
Page 53 and 54: Each view adds a listener to the co
Page 55 and 56: LoginController which also observes
Page 57 and 58: tends the JPanel class. The templat
Page 59: 7 EvaluationIn the previous chapter
Page 63 and 64: Figure 7.1: Latency of receiving da
Page 65 and 66: For this thesis only a rough estima
Page 67 and 68: Laptop CPU load without Probe CPU l
Page 69 and 70: 8 ConclusionsIn the context of this
Page 71 and 72: 9 OutlookGiven this new tool its no
Page 74: BibliographyBurrell, A. and A. Soda
Page 77 and 78: 6.10 Main classes of the Java clien
Page 79 and 80: AppendixUse CasesUse Case 1: Connec
Page 81 and 82: Use Case 4: Disconnect from compone
Page 83 and 84: Use Case 9: Sending beacon to keep
Page 85 and 86: Figure 9.4: Latency of receiving da
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