Context Switch in Reconfigurable System Sun, Yuan-Ling ESL of CSIE, CCU

Outline Introduction Context Switch Conclusions

Outline Introduction Context Switch Conclusions

Introduction What is context? Software: CPU registers, process state and memory management information … (stored in process control block ) Hardware: configuration (function) [David I. Lehn, Kiran Puttegowda, Jae H. Park, Peter M. Athanas, Mark T. Jones, "Evaluation of rapid context switching on a CSRC device,"Evaluation of rapid context switching on a CSRC device Proceedings of the International Conference on Engineering of Reconfigurable Systems and Algorithms, ]

The states of process States ： new 、 ready 、 running 、 waiting and terminated 。

The states of Configuration States: new 、 ready ( reservation) 、 running and terminated. [Christoph Steiger, Herbert Walder, Marco Platzner Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of Real-time Tasks ， IEEE Transactions on Computers, 53(11): , November 2004 ] All tasks are stored in state queue. (for scheduler)

Process Data Structure Software: process control block

Configuration Data Structure Hardware : Configuration control block task state ， PID ， registers … area size (gate count) arrival time ， execute time ， deadline

Tables FPGA information table ： FPGA total size ， free size ， task location ， task start time ， task terminal time ， routing. (for scheduler ， partition) Object translation table ： accessible SW/HW object. (for communication)

Outline Introduction Context Switch Conclusions

Context Switching Software definition: When CPU switches to another process, the system must save the state of the old process and load the saved state for the new process. Hardware definition: The configuration activation process is known as context switching. How to map the SW/HW context switch?

Hardware Context Switching Kiran Puttegowda, David I. Lehn, Jae H. Park, Peter Athanas, Mark Jones, "Context Switching in a Run-Time Reconfigurable System" The Journal of Supercomputing, Volume 26 Issue 3, November 2003Context Switching in a Run-Time Reconfigurable System

Why needs context switching Resource: CPU time quantum limit : SW  SW FPGA area limit: HW->HW Performance ： SW  HW Low power ： HW  SW (SW  HW??)

Switch point (quiescent state) How to find switch point? Using Hot-swapping

Hot-swapping Algorithm Establish a quiescent state. Transfer the component state between the old and the new object. Update the reference to the component.

What we can use ? Object translation table Mediator Quiescent state Call count reaches zero. State transfer Preserve as much of the original state and semantics as possible.

Indirection

Mediator Forward Block Completed

Outline Introduction Context Switch Conclusions

Define hardware context. Define hardware context switch. Using hot swapping to find switch point. Future work Communication issue Implementation problem