Load Latency Tolerance in Dynamically Scheduled Processors

This paper provides quantitative measurements of load latency tolerance in a dynamically scheduled processor. To determine the latency tolerance of each memory load operation, our simulations use flexible load completion policies instead of a fixed memory hierarchy that dictates the latency. Although our policies delay load completion as long as possible, they produce performance (instructions committed per cycle (IPC)) comparable to an ideal memory system where all loads complete in one cycle. Our measurements reveal that to produce IPC values within 8% of the ideal memory system, between 1% and 62% of loads need to be satisfied within a single cycle and that up to 84% can be satisfied in as many as 32 cycles, depending on the benchmark and processor configuration. Load latency tolerance is largely determined by whether an unpredictable branch is in the load's data dependence graph and the depth of the dependence graph. Our results also show that up to 36% of all loads miss in t...

• Type: Conference
• Year: 1998
• Where: MICRO
• Authors: Srikanth T. Srinivasan, Alvin R. Lebeck
• Keywords: Hardware, Latency Tolerance, Load Completion, Load Latency Tolerance, MICRO 1998