Informing Loads: Enabling Software to Observe and React to Memory Behavior
Mark Horowitz, Margaret Martonosi, Todd C. Mowry, Michael D. Smith · 1995
Memory latency is an important bottleneck in system performance that cannot be adequately solved by hardware alone. Several promising software techniques have been shown to address this problem success-fully in specific situations. However, the generality of these software approaches has been limited because current architectures do not provide a fine-grained, low-overhead mechanism to observe memory behavior directly. To fill this need, we propose a new set of memory operations called informing memory operations, and in particular, we describe the design and functionality of an informing load instruction. This instruction serves as a primitive that allows the software to observe cache misses and to act upon this information inex-pensively (i.e. under the miss, when the processor would typically be idle) within the current software con-text. Informing loads enable new solutions to several important software problems. We demonstrate this through examples that show their usefulness in (i) the collection of fine-grained memory profiles with high precision and low overhead and (ii) the automatic improvement of memory system performance through compiler techniques that take advantage of cache-miss information. Overall, we find that the apparent bene-