| This thesis summarizes the research and development efforts conducted in the past 2 years on extending Preempt-RT. It covers the contribution of this work along with the analysis of the technological principles behind Preempt-RT-notably in the context of MIPS. Further this thesis covers the specifics of the porting to the Loongson 2F platform and concludes with benchmark results and a performance analysis.The Preempt-RT effort, launched by Ingo Molnar in 2006, has been a patch to the mainline Linux kernel. This patch has been incorporating efforts by other groups (KURT, RED-Linux, low-latency) along the way and in many ways is a unification effort to bring real-time to mainline Linux. With the current Preempt-RT patch, mainine Linux truely is entering the RTOS domain and provides a full POSIX API. Preempt-RT is a full featured Linux extension, providing the full feature set of GNU/Linux including the network and graphical environment, extensive filesystem support, etc. Its souce code is released under GPL, freely downloadable, open to modification and portable-with support for x86, PowerPC, ARM, etc. Preempt-RT is still under development, and its full merge into mainline will still take some time, as such it currently does not yet support all platforms that Linux supports, but with this work MIPS has been added back to the list of architectures supported in Preempt-RT.Based on the investigation of its research progress and development trend, this work studied the latest source code of Preempt-RT and analyzed the core real time technologies notably:low-latency patch/voluntary preemption patch, preemption patch, interrupt threading, high resolution timer sub-system, real time scheduling policy, preemptible critical sections, priority inheritance and the related real time debugging and optimizing technologies:Ftrace and Perf. Through this work the author has achieved a well founded understanding of the principle and features of real time operating system in general and the specific implementation in mainline Linux more deeply.The target CPU for this work is the Loongson processor which is a processor developed in china. Its 1st revision, the loongson 1A, was released in 2002 and now stands at the transition to the third generation extending the Loongson to 64bit multicore CPUs. The revision most used in the market currently is the Loongson-2F, a MIPS compatible RISC architecture with a performance comparative to the Pentium V though at conciderably lower power-consumption. It has been used in the market of desktop, netbook and small servers, including NAS. Although it has low power consumption and thus is potentially suitable for the application in industrial automation, digital control as well as automotive electronics and other areas, exploitation in these areas all need the support of a real time operating system.The main goal of this work was porting Preempt-RT to the Loongson platform. This not only proved that Preempt-RT patch is highly portable but also provided a safe, reliable and efficient real time operating system for the Loongson 2F CPU. This not only brings MIPS support back to Preempt-RT but also potentially expanded the application of the MIPS processor and specifically the Loongson 2F in the above areas and even others such as national defence and Aero-space.This research project has been supported by Lemote and has in the meantime been accepted by the maintainer of Preempt-RT: git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git rt/2.6.33The latest research results are published and maintained under terms of GPL on the following sites:1.http://dslab.lzu.edu.cn/dslabwiki/index.php/Real_Time_Preempt_Patch(RT_PREE MPT)_for_MIPS2.http://dev.lemote.com/code/rt4ls... |
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