System and method for performing efficient hardware context switching in an instrumentation system

摘要

A system and method for performing more efficient hardware context switches in a computer-controlled instrumentation system including a computer system which controls a plurality of instruments. The instrumentation system includes a direct memory access transfer device which performs various data transfers between the computer system and the various instruments. The direct memory access transfer device includes different hardware contexts for different transfers, and the DMA transfer device automatically configures itself to different contexts with minimal CPU involvement. For each process or thread requiring a different DMA transfer device context, the CPU prepares the context information and stores the context in memory. The CPU then provides a request list to the DMA transfer device including interleaved context pointers and data transfer packets. When the DMA transfer device is performing transfers and needs to switch to a new context, the DMA transfer device reads the context from memory and automatically configures itself. Since, the context is stored in memory and hence readily available, the DMA transfer device does not have to interrupt the CPU to receive a new context. Once the CPU has prepared and stored the context information and provided the address of the context information to the DMA transfer device, the DMA transfer device can switch between contexts for transfers corresponding to different processes or threads numerous times without CPU involvement, thus increasing system efficiency.