Parallelism-Aware Memory Interference Delay Analysis for COTS Multicore Systems

In modern Commercial Off-The-Shelf (COTS) multicore systems, each core can generate many parallel memory requests at a time. The processing of these parallel requests in the DRAM controller greatly affects the memory interference delay experienced by running tasks on the platform. In this paper, we present a new parallelism-aware worst-case memory interference delay analysis for COTS multicore systems. The analysis considers a COTS processor that can generate multiple outstanding requests and a COTS DRAM controller that has a separate read and write request buffer, prioritizes reads over writes, and supports out-of-order request processing. Focusing on LLC and DRAM bank partitioned systems, our analysis computes worst-case upper bounds on memory-interference delays, caused by competing memory requests. We validate our analysis on a Gem5 full-system simulator modeling a realistic COTS multicore platform, with a set of carefully designed synthetic benchmarks as well as SPEC2006benchmarks. The evaluation results show that our analysis produces safe upper bounds in all tested benchmarks, while the current state-of-the-art analysis significantly under-estimates the delays.