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Main-memory multicore transactional systems have achieved excellent performance using single-version optimistic concurrency control (OCC), especially on uncontended workloads. Nevertheless, systems based on other concurrency control protocols, such as hybrid OCC/ locking and variations on multiversion concurrency control (MVCC), are reported to outperform the best OCC systems, especially with increasing contention. This paper shows that implementation choices unrelated to concurrency control can explain some of these performance differences. Our evaluation shows the strengths and weaknesses of OCC, MVCC, and TicToc concurrency control under varying workloads and contention levels, and the importance of several implementation choices called basis factors. Given sensible basis factor choices, OCC performance does not collapse on high-contention TPC-C. We also present two optimization techniques, deferred updates and timestamp splitting, that can dramatically improve the high-contention performance of both OCC and MVCC. These techniques are known, but we apply them in a new context and highlight their potency: when combined, they lead to performance gains of 4.74× for MVCC and 5.01× for OCC in a TPC-C workload.
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Obladi: Oblivious Serializable Transactions in the Cloud
This paper presents the design and implementation of Obladi, the first system to provide ACID transactions while also hiding access patterns. Obladi uses as its building block oblivious RAM, but turns the demands of supporting transac- tions into a performance opportunity. By executing transac- tions within epochs and delaying commit decisions until an epoch ends, Obladi reduces the amortized bandwidth costs of oblivious storage and increases overall system through- put. These performance gains, combined with new oblivious mechanisms for concurrency control and recovery, allow Obladi to execute OLTP workloads with reasonable through- put: it comes within 5× to 12× of a non-oblivious baseline on the TPC-C, SmallBank, and FreeHealth applications. Latency overheads, however, are higher (70× on TPC-C).
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- Award ID(s):
- 1762015
- PAR ID:
- 10082091
- Date Published:
- Journal Name:
- Proceedings of the 13th USENIX Symposium on Operating Systems Design and Implementation (OSDI ’18)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
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