Preemptive Hardware Multitasking in ReconOS

Preemptive hardware multitasking is not supported in most reconfigurable systems-on-chip (rSoCs), which severely limits the scope of hardware scheduling techniques on these platforms. While modern field-programmable gate arrays (FPGAs) support dynamic partial reconfiguration of any region at any time, most hardware tasks cannot be preempted at arbitrary points in time, because context saving and restoring is not supported out of the box by the vendors. Although hardware task preemption techniques have been proposed in the past, they cannot be found in today’s rSoCs. In this paper we therefore propose a novel methodology for preemptive hardware multitasking that does not require any changes at the task level and show that our approach can be seamlessly integrated to an established execution environment for rSoCs, called ReconOS. Our experimental results show that we can successfully capture and restore the states of all flip-flops and block RAMs in a reconfigurable region on a Xilinx Virtex-6 FPGA at arbitrary points in time. Context capturing/restoring can be performed at a bandwidth of 2228MB/s, which allows for context switches in the order of milliseconds.