Data Prefetching Optimization Research In Dynamic Binary Translation Based Loongson Virtual Machine

As software means of code migration, binary translation can convert executable binaries in the absence of its sources from one instruction set architecture to the other. Dynamic binary translation is just-in-time translation, while at the same time, it can do dynamic optimization. With the progress of processor,compiler technology, binary translation has become a hot research direction and has got extensive attention in virtualization technology,distributed computing and information security, et al. Currently, the rate of improvement in microprocessor speed exceeds the rate of improvement in Dynamic Random Access Memory speed. Hence the increasing Processor-Memory Performance Gap is now the primary obstacle to improved computer system performance. Dynamic optimization is an important research subject in binary translation systems. As a way of memory optimization, data prefetching reads subsequent data into high speed caches ahead of time to hide memory access latency, which can improve application's performance.In this thesis, data prefetching optimization is studied for the first time in a binary translation system. It combines Loongson processor's hardware features and uses software instrumentation to collect program's memory access latency information. Firstly, delinquent loads and their types are identified, data prefetching optimization unit—SuperBlocks are then constructed from frequently executed code blocks, after that, basic prefetching optimization is realized. Secondly, the data flow analysis is performed on SuperBlock to generate the RDUG(register define and use graph), and then some data prefetching schemes are proposed based on load instructions'address computing components.Experiments on the dynamic binary translation based Loongson-3 virtual machine show that, Superblock construction can achieve 10% improvement on average for translated SPEC2000 int programs while the overhead is less than 1%. Although data prefetching optimization has lettle effect on SPEC2000 int, it can improve the performance of SPEC2000 float programs by 3.3% on average with the analysis overhead far less than 0.5%.