A Software-Controlled Cache Coherence Optimization for Snoopy-Based SMP System

Some research results show that on average 67% of broadcasts for the maintenance of cache coherence in SMP systems are unnecessary. To reduce the unnecessary overhead of snoopy-based SMP systems, this paper proposes a new software/hardware hybrid cache coherence optimization-the programmer can insert special instructions into programs to direct related hardware to enable/disable broadcast operations, so some potential broadcasts for unshared variables are avoided without violating data coherence. We design the mechanism along with a proposed coherence protocol. Moreover, it is simulated on a SMP simulation platform and the results show that the improvement is apparent. Although the insertion is manual, it accords with the existing SMP programming model.