CoreRank: Redeeming "Sick Silicon" by Dynamically Quantifying Core-Level Healthy Condition

In field degradation of manycore processors poses a grand challenge to core management, largely because the degradation is hard to quantify. We propose a novel core-level degradation quantification scheme, CoreRank, to facilitate the management. We first develop a new degradation metric, called "healthy condition", to capture the implication of performance degradation of a core with specific degraded components. Then, we propose a performance sampling scheme by using micro-operation streams, called snippet, to statistically quantify cores' healthy condition. We find that similar snippets exhibit stable performance distribution, which makes them ideal micro-benchmarks to testify the core-level healthy conditions. We develop a hardware-implemented version of CoreRank based on bloom filter and hash table. Unlike the traditional "faulty" or "fault-free" judgement, CoreRank provides a key facility to make better use of those imperfect cores that suffered from various progressive aging mechanisms such as NBTI, HCI. Experimental results show that CoreRank successfully hides significant performance degradation of a defective manycore processor in which even more than half of the cores are salvaged from various defects.