Chapter 4 - DSpace at Waseda University

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Chapter 6 In embedded systems, there are a lot of errors and bugs. Some errors and bugs are solved easily. However, there are a lot of complicated problems such as memory leak and timer latency. In addition, it is not easy to find where the problem has occurred and how a developer or system manager fixes the problems up so as to improve the performance of system. Every embedded kernel generates event information such as irq, system call, I/O, memory and network It is the event information that is the one of the most useful solution to analyze the cause of a problem in embedded systems to improve the performance. However, there is another problem that the event information is huge. Therefore, to analyze all the event information is not easy and not effective. We propose a new system architecture which analyzes the event log through the embedded kernel - KAS. The KAS finds out problems through the kernel exceedingly quickly, and separates them from the whole event information. And then, it starts to analyze them statistically and provides a developer or system manager with the recommended solution. In a case study, we tested HRTimer’s latency, and got a result that the cause of HRTimer’s latency is usually coming from softirq priority. However, only by solving the priority problem, the HRTimer’s latency problem is not able to be settled perfectly since sometimes it is caused by hardirq’s latency or latency at an interrupt locking. However, we examined how effective and quick to solve problems at an embedded kernel by using the KAS. 6.2 Future Work In this section, we describe problems of the KAS, and explain how to improve it. Actually, the KAS does not support real-time analysis. In addition, it needs to improve to be connected 78
an accounting system that is able to control processes. 6.2.1 Real-Time Architecture of KAS 79 Chapter 6 KAS starts to analyze at the end of event log information. This can be a problem because it needs to save all the event log information first. In addition, problems can not be prevented in advance because KAS detects problems from the event log information. From these reasons, there are two main problems in KAS. First, it is not easy to analysis problem because the event log information is huge. Second, it can not be prevented in advance. To improve the KAS, we need to decrease of the event log information not by saving all the information but by saving only the part of the problem in real-time. This can be very helpful to decrease workload of a system and, save time for analyzing SL and AL at KAS. In Figure 6.1, KAS is the real-time architecture model of KAS. It checks problems through KAS daemon in real-time. If problems have detected, KAS saves only the part of the event log information which problems has occurred, and analyzes them by using SL and AL. 6.2.2 KAS and CABI We tested the HRTimer latency at the case study. From the result of the case study, there are some processes that occupied all of the CPU usage or timer latency in the Linux kernel. Therefore, if KAS finds out a process which occupies CPU usage too much, it sends the process id to an accounting system. The accounting system [50] can manage the CPU usage
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Analyzing Real-Time Performance Pro
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to propose a solution for the probl
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2.5 Event Log …………………
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6. Conclusions and Future Work 6.1
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List of Figures 2.1 User-space vs.
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5.12: One of the reasons of HRTimer
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Chapter 1 functions or equipped wit
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Chapter 1 huge losses in cost. For
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Chapter 1 1.3 Contribution When dev
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Chapter 2 Background 2.1 Embedded S
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Chapter 2 memory and to manage syst
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Chapter 2 2.3 Embedded Linux An emb
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Chapter 2 � How often CPU accesse
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Chapter 2 2.6 Problem Analysis Figu
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Chapter 2 � To count time accurat
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Chapter 2 board. Its clock signal i
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Chapter 3 hardware such as SoC (Sys
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Chapter 3 shows how useful the logg
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Chapter 3 free to check memory. How
Page 40 and 41: Chapter 3 Figure 3.3: Process viewe
Page 42 and 43: Chapter 3 In Figure 3.4, through Me
Page 44 and 45: Chapter 3 Figure 3.6: Event logging
Page 46 and 47: Chapter 4 execution times, and whol
Page 48 and 49: Chapter 4 due to its large amount.
Page 50 and 51: Chapter 4 Advantage of analysis by
Page 52 and 53: Chapter 4 ways of debugging accordi
Page 54 and 55: Chapter 4 problem has occurred it f
Page 56 and 57: Chapter 4 4.2.2 Separation Layer Fi
Page 58 and 59: Chapter 4 4.2.3 Analysis Layer Figu
Page 60 and 61: Chapter 4 and a developer analyzes
Page 62 and 63: Chapter 4 Table 4.1: Important para
Page 64 and 65: Chapter 4 possible to event logging
Page 66 and 67: Chapter 4 KAS’s dependency with L
Page 68 and 69: Chapter 5 5.1 Timer Latency When a
Page 70 and 71: Chapter 5 mode [31]. In opposite, p
Page 72 and 73: Chapter 5 Figure 5.4 shows the inte
Page 74 and 75: Chapter 5 latency. Figure 5.5 shows
Page 76 and 77: Chapter 5 Figure 5.6 Interface of s
Page 78 and 79: Chapter 5 Table 5.1: Result of Dete
Page 80 and 81: Chapter 5 Table 5.2: Result of Anal
Page 82 and 83: Chapter 5 most of time. Especially,
Page 84 and 85: Chapter 5 Figure 5.13: Result of an
Page 86 and 87: Chapter 5 Figure 5.16: Result of ex
Page 88 and 89: Chapter 5 5.6 Summary We analyzed l
Page 92 and 93: Chapter 6 Figure 6.1: Real-Time Arc
Page 94 and 95: Appendix A.1 RTOS Commonly, a goal
Page 96 and 97: Appendix software, real-time OS mus
Page 98 and 99: Appendix critical task and non-crit
Page 100 and 101: Appendix � Portability CABI shoul
Page 102 and 103: Bibliography [1] L. Abeni, A. Goel,
Page 104 and 105: Bibliography [21] C. Yuan, N. Lao,
Page 106 and 107: Bibliography [38] Magdalena Balazin
Page 108 and 109: Bibliography [56] Balakrishnan, S.;
Page 110 and 111: Acknowledgements I would firstly li
Page 112 and 113: Publication List 種類別題名
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