MONTRES-NVM: An External Sorting Algorithm for Hybrid Memory

DRAM technology is approaching its scaling limit and the use of emerging NVM is seen as one possible solution to such an issue. As NVM technologies are not mature enough and does not outperform DRAMs, several studies expect the use of hybrid main memories containing both DRAM and PCM NVM. Redesigning applications for such systems is mandatory as PCM does not have the same performance model as DRAM. In this context, we designed a hybrid memory-aware sorting algorithm called MONTRES-NVM. Since an NVM-based hybrid memory presents a performance gap between DRAM and PCM, we believe that the sorting algorithm falls in the external sorting category. As a matter of fact, we extended our previously designed flash-based external sorting algorithm MONTRES for a hybrid memory by taking profit of byte addressability, and performance asymmetry between reads and writes. MONTRES-NVM enhances the performance of the merge sort algorithm on PCM by more than 60%, the merge sort on DRAM by 3-40% and MONTRES (on a hybrid memory) by 3-33% according to the proportion of already sorted data in the dataset.