Hybrid main memory architectures employing both DRAM and non-volatile memories (NVMs) are becoming increasingly attractive due to the opportunities for exploring benefits of various memory technologies, for example, high speed writes on DRAM and low stand-by power consumption on NVMs. File data-block placement (FDP) on different types of page cache is one of the important problems that directly impact the performance and cost of file operations on a hybrid main memory architecture. Page cache is widely used in modern operating systems to expedite file I/O by mapping disk-backed file data-blocks in main memory to process space in virtual memory. In a hybrid main memory, different types of memory with different read/write costs can be allocated as page cache by operating system. In this paper, we study the problem of file data-block placement on different types of page cache to minimize the total cost of file accesses in a program. We propose a dynamic programming algorithm, the FDP Algorithm, to solve the problem optimally for simple programs. We develop an ILP model for the file data-block placement problem for programs composed of multiple regions with data dependencies. An efficient heuristic, the global file data-block placement (GFDP) Algorithm, is proposed to obtain near-optimal solutions for the problem of global file data-block placement on hybrid main memory. Experiments on a set of benchmarks show the effectiveness of the GFDP algorithm compared with a greedy strategy and the ILP. Experimental results show that the GFDP algorithm reduces the total cost of file accesses by 51.3 on average compared with the the greedy strategy.
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