Shenandoah

Flood, Christine H.; Kennke, Roman; Dinn, Andrew; Haley, Andrew G.; Westrelin, Roland

doi:10.1145/2972206.2972210

Cited by 41 publications

(6 citation statements)

References 11 publications

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“…Although our stop-the-world minor collector scaled up admirably to at least 24 cores, synchronisation costs will inevitably increase as the number of cores do. Adding a read barrier (as used by the concurrent minor collector) opens up the GC design space considerably; for example to add a pauseless algorithm [Click et al 2005] such as the ones used in modern Java GCs like Azul, ZGC [Tene et al 2011] or Shenandoah [Flood et al 2016]. Our results for the concurrent minor collector show that the read barrier has less overhead in OCaml code than initially expected, and would be a reasonable solution in many-core machines.…”

Section: Related Workmentioning

confidence: 64%

Retrofitting parallelism onto OCaml

Sivaramakrishnan

Dolan²,

White³

et al. 2020

Proc. ACM Program. Lang.

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OCaml is an industrial-strength, multi-paradigm programming language, widely used in industry and academia. OCaml is also one of the few modern managed system programming languages to lack support for shared memory parallel programming. This paper describes the design, a full-fledged implementation and evaluation of a mostly-concurrent garbage collector (GC) for the multicore extension of the OCaml programming language. Given that we propose to add parallelism to a widely used programming language with millions of lines of existing code, we face the challenge of maintaining backwards compatibilityśnot just in terms of the language features but also the performance of single-threaded code running with the new GC. To this end, the paper presents a series of novel techniques and demonstrates that the new GC strikes a balance between performance and feature backwards compatibility for sequential programs and scales admirably on modern multicore processors. CCS Concepts: • Software and its engineering → Garbage collection; Parallel programming languages.

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Section: Related Workmentioning

confidence: 64%

Retrofitting parallelism onto OCaml

Sivaramakrishnan

Dolan²,

White³

et al. 2020

Proc. ACM Program. Lang.

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“…If it fails, the relocation is aborted, and the speculative copy is freed, as some other thread has pinned that handle while the copy was being made. We see it as an interesting path forward to implement concurrent memory movement, as this closely resembles the concurrent compaction system seen in the Shenandoah GC [28]. This simple mechanism could be utilized to implement swapping objects to disk, compression, or even far memory.…”

Section: Discussionmentioning

confidence: 92%

Getting a Handle on Unmanaged Memory

Wanninger,

McMichen,

Campanoni

et al. 2024

Proceedings of the 29th ACM International Conference on Architectural Support for Programming Languages and Operating Systems,

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The inability to relocate objects in unmanaged languages brings with it a menagerie of problems. Perhaps the most impactful is memory fragmentation, which has long plagued applications such as databases and web servers. These issues either fester or require Herculean programmer effort to address on a per-application basis because, in general, heap objects cannot be moved in unmanaged languages. In contrast, managed languages like C# cleanly address fragmentation through the use of compacting garbage collection techniques built upon heap object movement. In this work, we bridge this gap between unmanaged and managed languages through the use of handles, a level of indirection allowing heap object movement. Handles open the door to seamlessly employing runtime features from managed languages in existing, unmodified code written in unmanaged languages. We describe a new compiler and runtime system, Alaska, that acts as a drop-in replacement for malloc. Without any programmer effort, the Alaska compiler transforms pointer-based code to utilize handles, with optimizations to minimize performance impact. A codesigned runtime system manages this new level of indirection and exploits heap object movement via an extensible service interface. We investigate the overheads of Alaska on large benchmarks and applications spanning multiple domains. To show the power and extensibility of handles, we use Alaska to eliminate fragmentation on the heap through defragmentation, reducing memory usage by up to 40% in Redis.

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“…In these systems, mutator loads, stores, and/or uses of references are subject to barriers to preserve collector invariants. Decades of research into collectors have yielded a plethora of barrier designs [8,14,15,18,19,24,28,29,31,40,41,59].…”

Section: Analogous Barriers In Garbage Collectionmentioning

confidence: 99%

Cornucopia Reloaded: Load Barriers for CHERI Heap Temporal Safety

Filardo,

Gutstein,

Woodruff

et al. 2024

Proceedings of the 29th ACM International Conference on Architectural Support for Programming Languages and Operating Systems,

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Violations of temporal memory safety ("use after free", "UAF") continue to pose a significant threat to software security. The CHERI capability architecture has shown promise as a technology for C and C++ language reference integrity and spatial memory safety. Building atop CHERI, prior works -CHERIvoke and Cornucopia -have explored adding heap temporal safety. The most pressing limitation of Cornucopia was its impractical "stop-the-world" pause times.We present Cornucopia Reloaded, a re-designed drop-in replacement implementation of CHERI temporal safety, using a novel architectural feature -a per-page capability load barrier, added in Arm's Morello prototype CPU and CHERI-RISC-V -to nearly eliminate application pauses. We analyze the performance of Reloaded as well as Cornucopia and CHERIvoke on Morello, using the CHERI-compatible SPEC CPU2006 INT workloads to assess its impact on batch workloads and using pgbench and gRPC QPS as surrogate interactive workloads. Under Reloaded, applications no longer experience significant revocation-induced stop-the-world periods, without additional wall-or CPU-time cost over Cornucopia and with median 87% of Cornucopia's DRAM traffic overheads across SPEC CPU2006 and < 50% for pgbench.CCS Concepts • Software and its engineering → Software safety; • Security and privacy → Operating systems security; • Hardware → Emerging architectures.

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Shenandoah

Cited by 41 publications

References 11 publications

Retrofitting parallelism onto OCaml

Retrofitting parallelism onto OCaml

Getting a Handle on Unmanaged Memory

Cornucopia Reloaded: Load Barriers for CHERI Heap Temporal Safety

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