Reducing LDPC soft sensing latency by lightweight data refresh for flash read performance improvement

In order to relieve reliability problem caused by technology scaling, LDPC codes have been widely applied in flash memories to provide high error correction capability. However, LDPC read performance slowdown along with data retention largely weakens the access speed advantage of flash memories. This paper considers to apply the concept of refresh, that were used for flash lifetime improvement, to optimize flash read performance. Exploiting data read characteristics, this paper proposes LDR, a lightweight data refresh method, that aggressively corrects errors in read-hot pages with long read latency and reprograms error-free data into new pages. Experimental results show that LDR can achieve 29% read performance improvement with only 0.2% extra P/E cycles on average, which causes negligible overhead on flash lifetime.