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ISMM 2018
co-located with PLDI 2018

We present FRC, a high-performance concurrent parallel reference counter for unmanaged languages. It is well known that high-performance garbage collectors help developers write memory-safe, highly concurrent systems and data structures. While C++, C, and other unmanaged languages are used in high-performance applications, adding concurrent memory management to these languages has proven to be difficult. Unmanaged languages like C++ use pointers instead of references, and have uncooperative mutators which do not pause easily at a safe point. Thus, scanning mutator stack root references is challenging.

FRC only defers decrements and does not require mutator threads to pause during collection. By deferring only decrements, FRC avoids much of the synchronization overhead of a fully-deferred implementation. Root references are scanned without interrupting the mutator by publishing these references to a thread-local array. FRC's performance can exceed that of the C++ standard library's shared pointer by orders of magnitude. FRC's thread-safety guarantees and low synchronization overhead enable significant throughput gains for concurrently-readable shared data structures.

We describe the components of FRC, including our static tree router data structure: a novel barrier which improves the scalability of parallel collection workers. FRC's performance is evaluated on several concurrent data structures. We release FRC and our tests as open-source code and expect FRC will be useful for many concurrent C++ software systems.

Mon 18 Jun

ismm-2018-papers
10:45 - 12:15: ISMM 2018 - Reference Counting and Techniques for C-family Languages at Discovery AB
Chair(s): Emery BergerUniversity of Massachusetts, Amherst
ismm-2018-papers10:45 - 11:15
Talk
Stuart BymaEPFL, Switzerland, James LarusEPFL
ismm-2018-papers11:15 - 11:45
Talk
Charles TrippTerrain Data, USA, David HydeStanford University, USA, Benjamin Grossman-PonemonTerrain Data, USA
ismm-2018-papers11:45 - 12:15
Talk
Steven R. BrandtLouisiana State University, Hari KrishnanFacebook, n.n., Costas BuschLouisiana State University, USA, Gokarna SharmaKent State University, USA