Improving scratch-pad memory reliability through compiler-guided data block duplication

Recent trends in embedded computing indicates an increasing use of scratch-pad memories (SPMs) as on-chip store for instructions and data. An important characteristic of these memory components is that they are managed by software, instead of hardware. Ever-scaling process technology and employment of several power-saving techniques in embedded systems (e.g., voltage scaling) make these systems particularly vulnerable to soft errors and other transient errors. Therefore, it is very important in practice to consider the impact of soft errors in SPMs. While it is possible to employ classical memory protection mechanisms such as parity checks and ECC, each of these has its drawbacks. Specifically, a pure parity-based protection cannot correct any errors, and ECCs can be an overkill in the normal operation state when no soft error is experienced. This paper proposes an alternate approach to protect SPMs against soft errors. The proposed approach is based on data block duplication under compiler control. More specifically, an optimizing compiler duplicates data blocks within the SPM and protects each data block by parity if such a duplication does not hurt performance. The goal of this scheme is to provide only parity protection for data blocks (and reduce the overheads at runtime when no error occurs) but correct errors using the duplicate (when an error occurs in the primary copy), provided that the duplicate is not corrupted.