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Li C.-M.,Tsinghua University | Li C.-M.,Tsinghua Laboratory for Information Science and Technology | Wang H.-X.,Tsinghua University | Wang H.-X.,Tsinghua Laboratory for Information Science and Technology | And 4 more authors.
Jisuanji Xuebao/Chinese Journal of Computers | Year: 2011

As more cores are integrated into one die, chip multiprocessors suffers higher on-chip communication latency, and linearly increased directory overheard. Hierarchical cache architecture partitions on-chip caches into multilevel regions recursively, reducing the communication latency by replicating the data blocks to multiple regions that contains the requestor and alleviating the storage overhead of directory by using multilevel directory. According to the data distribution in the last-level cache, we improve the data placement policy and propose an enhanced hierarchical cache directory (EHCD). EHCD directly puts an incoming off-chip data block into the lowest region that contains the requestor to reduce access latency, which guarantees only one data replica is kept in the last-level cache for private data. EHCD improves the capacity utilization of the last-level cache as well as good scalability. Simulation results on a 16-core CMP show that compared with shared organization, EHCD gets 24% execution time reduction, and 15% reduction over original hierarchical cache design. Source

Wang J.-M.,Tsinghua University | Wang J.-M.,Tsinghua Laboratory for Information Science and Technology | Wang J.-M.,Key Laboratory for Information System Security of Ministry of Education | Yu Z.-W.,Tsinghua University | And 8 more authors.
Jisuanji Xuebao/Chinese Journal of Computers | Year: 2011

Obfuscation techniques have been widely applied in the defenses of reverse engineering and re-engineering attacks. From the view of the development of obfuscation, we briefly discussed the principles, algorithms, different kinds of attack approaches and evaluating standard. Java program obfuscation algorithms can be divided into two types: One is obfuscation within a class; the other is obfuscation between classes. Finally, based on the survey of these obfuscation techniques, the future research of Java program obfuscation is also stated. Source

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