Work-in-Progress: Prediction-based Fine-Grained LDPC Reading to Enhance High-Density Flash Read Performance

Abstract

LDPC codes have been widely applied in high-density flash memories, e.g., TLC flash and QLC flash, to ensure data reliability. In order to reduce the read latency of high-density flash memories, this paper proposes a prediction-based fine-grained LDPC reading method, named as PreLDPC. From a preliminary study, we observe that the ratio of cells that lie in error-prone areas (i.e., the areas between two adjacent cell states) is closely related to the final read level for successful decoding. Based on this observation, PreLDPC predicts the read level for LDPC reading, which could avoid excessive unnecessary read-retries. Furthermore, a fine-grained read method with fine sub-levels is used in the read-retry iteration for read latency reduction. From experimental results over real-world workloads on Disksim with SSD extensions, the effectiveness of PreLDPC on reducing read latency is verified in high-density flash memories.