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Register a new userCache-Aware Lock-Free Concurrent Hash Tries
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Added by
Aleksandar Prokopec
Publication date
2017
fields
Informatics Engineering
and research's language is
English
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This report describes an implementation of a non-blocking concurrent shared-memory hash trie based on single-word compare-and-swap instructions. Insert, lookup and remove operations modifying different parts of the hash trie can be run independent of each other and do not contend. Remove operations ensure that the unneeded memory is freed and that the trie is kept compact. A pseudocode for these operations is presented and a proof of correctness is given -- we show that the implementation is linearizable and lock-free. Finally, benchmarks are presented which compare concurrent hash trie operations against the corresponding operations on other concurrent data structures, showing their performance and scalability.
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Ctrie is a scalable concurrent non-blocking dictionary data structure, with good cache locality, and non-blocking linearizable iterators. However, operations on most existing concurrent hash tries run in O(log n) time. In this technical report, we extend the standard concurrent hash-tries with an auxiliary data structure called a cache. The cache is essentially an array that stores pointers to a specific level of the hash trie. We analyze the performance implications of adding a cache, and prove that the running time of the basic operations becomes O(1).
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On Intel Sandy Bridge processor, last level cache (LLC) is divided into cache slices and all physical addresses are distributed across the cache slices using an hash function. With this undocumented hash function existing, it is impossible to implement cache partition based on page coloring. This article cracks the hash functions on two types of Intel Sandy processors by converting the problem of cracking the hash function to the problem of classifying data blocks into different groups based on eviction relationship existing between data blocks that are mapped to the same cache set. Based on the cracking result, this article proves that its possible to implement cache partition based on page coloring on cache indexed by hashing.
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