Chapter 4 - DSpace at Waseda University

More documents

Recommendations

Info

Chapter 5 Figure 5.4 shows the interrupt process in the non-preemptive kernel. Unlike the preemptive kernel, a low priority task keeps running even though high priority task occurs during the working of low priority task. After the low priority task ends, the kernel runs the high priority task. 5.3 High Resolution Timer We already have a timer subsystem (kernel/timers.c), why do we need two timer subsystems? Normally, the most fine-grained time supported by the timer in Linux kernel is 1ms. However, embedded Linux needs much more fine grained time. Therefore, any system engineers are trying to integrate high-resolution and high-precision features into the existing timer framework. However, general Linux timer cannot support accuracy of microseconds. HRTimer provides microsecond resolution with lower overhead and controls time more el aborately than other timer. It is not possible to use HRTimer in every system. To use HRTimer supported from hardware. The HRTimer system allows a user space program to be wake up from a timer event with better accuracy, when using the POSIX timer APIs. Without this system, the best accuracy that can be obtained for timer events is 1 jiffy. This depends on the setting of HZ in the kernel. In the 2.4 kernel, HZ was set to 100, which means that the best accuracy you could get on a timer wakeup in user space was 10 milliseconds. In other to use HRTimer needs as follows: � Need to verify that the kernel has support for this feature for your target processor (and board). 60
� Need to configure support for it in the Linux kernel. � Set CONFIG_HIGH_RES_TIMERS=y in kernel config. � Compile the kernel. The timer that support microsecond APIs are as follows: 61 Chapter 5 � timer_settime(): sets the time until the next expiration of the timer is specified by timer-id. � setitimer(): system provides each process with an interval timer. When the timer expires, a signal is sent to the process, and the timer expired. � nanosleep():set up high resolution sleep. � ualarm(): cause the SIGALRM signal to be generated for the calling process after the number of microseconds. � usleep(): cause the calling thread to be suspended from execution until either the number of real-time microseconds The HRTimer is not occurring timer interrupt periodically. The period of HRTimer can set up a programmer. 5.4 Latency Policy In this thesis, we describe about timer latency and policy of HRTimer to measure HRTimer
Page 1:
Analyzing Real-Time Performance Pro
Page 4 and 5:
to propose a solution for the probl
Page 6 and 7:
2.5 Event Log …………………
Page 8 and 9:
6. Conclusions and Future Work 6.1
Page 10 and 11:
List of Figures 2.1 User-space vs.
Page 12 and 13:
5.12: One of the reasons of HRTimer
Page 14 and 15:
Chapter 1 functions or equipped wit
Page 16 and 17:
Chapter 1 huge losses in cost. For
Page 18 and 19:
Chapter 1 1.3 Contribution When dev
Page 20 and 21:
Chapter 2 Background 2.1 Embedded S
Page 22 and 23: Chapter 2 memory and to manage syst
Page 24 and 25: Chapter 2 2.3 Embedded Linux An emb
Page 26 and 27: Chapter 2 � How often CPU accesse
Page 28 and 29: Chapter 2 2.6 Problem Analysis Figu
Page 30 and 31: Chapter 2 � To count time accurat
Page 32 and 33: Chapter 2 board. Its clock signal i
Page 34 and 35: Chapter 3 hardware such as SoC (Sys
Page 36 and 37: Chapter 3 shows how useful the logg
Page 38 and 39: 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 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 90 and 91: Chapter 6 In embedded systems, ther
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
show all

Chapter 4 - DSpace at Waseda University

Create successful ePaper yourself

Delete template?

Save as template?