Real-Time Multiprocessor Architecture for Sharing Stream Processing Accelerators

Stream processing accelerators are often applied in MPSoCs for software defined radios. Sharing of these accelerators between different streams could improve their utilization and reduce thereby the hardware cost but is challenging under real-time constraints. In this paper we introduce entry- and exit-gateways that are responsible for multiplexing blocks of data over accelerators under real-time constraints. These gateways check for the availability of sufficient data and space and thereby enable the derivation of a dataflow model of the application. The dataflow model is used to verify the worst-case temporal behaviour based on the sizes of the blocks of data used for multiplexing. We demonstrate that required buffer capacities are non-monotone in the block size. Therefore, an ILP is presented to compute minimum block sizes and sufficient buffer capacities. The benefits of sharing accelerators are demonstrated using a multi-core system that is implemented on a Virtex 6 FPGA. A stereo audio stream from a PAL video signal is demodulated in this system in real-time where two accelerators are shared within and between two streams. In this system sharing reduces the number of accelerators by 75% and reduced the number of logic cells with 63%.