Reducing Context Switch Overhead with Compiler-Assisted Threading

Multithreading is an important software modularization technique. However, it can incur substantial overheads, es-pecially in processors where the amount of architecturally visible state is large. We propose an implementation technique for co-operative multithreading, where context switches occur in places that minimize the amount of state that needs to be saved. The subset of processor state saved during each con-text switch is based on where the switch occurs. We have validated the approach by an empirical study of resource usage in basic blocks, and by implementing the co-operative threading in our compiler. Performance fig-ures are given for an MP3 player utilizing the threading implementation.