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Abstract Optimizing Memory Transactions
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@MISC{Harris_abstractoptimizing,
author = {Tim Harris and Mark Plesko and Avraham Shinnar and David Tarditi},
title = {Abstract Optimizing Memory Transactions},
year = {}
}
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Abstract
Atomic blocks allow programmers to delimit sections of code as ‘atomic’, leaving the language’s implementation to enforce atomicity. Existing work has shown how to implement atomic blocks over word-based transactional memory that provides scalable multiprocessor performance without requiring changes to the basic structure of objects in the heap. However, these implementations perform poorly because they interpose on all accesses to shared memory in the atomic block, redirecting updates to a thread-private log which must be searched by reads in the block and later reconciled with the heap when leaving the block. This paper takes a four-pronged approach to improving performance: (1) we introduce a new ‘direct access ’ implementation that avoids searching thread-private logs, (2) we develop compiler optimizations to reduce the amount of logging (e.g. when a thread accesses the same data repeatedly in an atomic block), (3) we use runtime filtering to detect duplicate log entries that are missed statically, and (4) we present a series of GC-time techniques to compact the logs generated by long-running atomic blocks. Our implementation supports short-running scalable concurrent benchmarks with less than 50 % overhead over a non-thread-safe baseline. We support long atomic blocks containing millions of shared memory accesses with a 2.5-4.5x slowdown. Categories and Subject Descriptors D.3.3 [Programming Languages]: Language Constructs and Features—Concurrent programming
Keyphrases
atomic block abstract optimizing memory transaction thread-private log long atomic block long-running atomic block short-running scalable concurrent benchmark subject descriptor basic structure gc-time technique scalable multiprocessor performance language implementation new direct access implementation language construct duplicate log entry programming language shared memory access runtime filtering feature concurrent programming non-thread-safe baseline compiler optimization word-based transactional memory four-pronged approach
