Study Of Porting Embedded Operating Systems Rte.ms Based On Multicore DSP

Multicore processors have already became mainstream and are being widely applied in embedded devices.That operating systems,as the interface of user applications and hardware,support for the multicore processors effectively is the key point to exploit the advantages of the performance of multicore processors.Current research on how operating systems support for the multicore processors has focus on tightly coupled and shared memory architecture,which is the most common architecture for multicore processors,but ignores other special memory architectures.In this paper,we study the multicore operating system model for memory-constrained and multi-level memory architecture based on multicore DSP BWDSP104x platform.Also,we complete porting RTEMS,which is a multicore embedded operating systems,to BWDSP104x.This study mainly includes the following aspects:(1)We analyze three traditional multiprocessing models of embedded operating systems in detail,namely asymmetric multiprocessing(AMP),symmetric multiprocessing(SMP)and bound multiprocessing(BMP),and point out each model's constraints of hardware platform and application requirements.Regarding the memory architecture of BWDSP104x,a new embedded multicore operating system model based on single code and multiple data(SCMD)is proposed.One OS code,merging from per-core OS code,is deployed on global shared code memory,while per-co.re OS data is deployed on private data memory with the same address space.Experiments show that,when applied to an eight-core DSP based on a multi-level memory architecture,this model can efficiently reduce the code space overhead by 80%compared to AMP;and the time cost related to real-time is ten times lower than that on SMP.(2)SCMD model,with highly portability,is easy for single-core embedded operating systems to port to multicore environment.RTEMS,an open source Real Time Operating System(RTOS),is ported to BWDSP104x in this paper.In response to the great number of registers in BWDSP104x,three strategies are proposed to optimize the cost of context switch and decrease the interrupt latency,improving the system's real time performance.To BWDSP104x,which doesn't support for the hardware interrupt stack,it's easy to take the task stack overflow when the system interrupt is nested too much.By adding an independent software interrupt stack,the stack pointer switches to the software interrupt stack,without using the task stack anymore,when the interrupt is triggered.Through this method,the system can effectively reduce the requirement of task stack space,and improve reliability and the throughput of interruption.