On the usefulness of type and liveness accuracy for garbage collection and leak detection

Hirzel, Martin; Diwan, Amer; Henkel, Johannes

doi:10.1145/586088.586089

Cited by 41 publications

(26 citation statements)

References 29 publications

(47 reference statements)

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“…Prior work has reported that even fully conservative GC rarely suffers from typeaccuracy problems on 64-bit architectures-although more issues have been reported on 32-bit architectures [32]. Other studies confirm that type accuracy is marginal compared to liveness accuracy [33]. In our context, liveness accuracy problems are only to be expected for uninstrumented allocator abstractions that aggressively use free lists-or other forms of reuse.…”

Section: Mutable Tracingmentioning

confidence: 49%

Mutable checkpoint-restart

Giuffrida

Iorgulescu

Tanenbaum

2014

Proceedings of the 15th International Middleware Conference on - Middleware '14

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The pressing demand to deploy software updates without stopping running programs has fostered much research on live update systems in the past decades. Prior solutions, however, either make strong assumptions on the nature of the update or require extensive and error-prone manual effort, factors which discourage live update adoption.This paper presents Mutable Checkpoint-Restart (MCR), a new live update solution for generic (multiprocess and multithreaded) server programs written in C. Compared to prior solutions, MCR can support arbitrary software updates and automate most of the common live update operations. The key idea is to allow the new version to restart as similarly to a fresh program initialization as possible, relying on existing code paths to automatically restore the old program threads and reinitialize a relevant portion of the program data structures. To transfer the remaining data structures, MCR relies on a combination of precise and conservative garbage collection techniques to trace all the global pointers and apply the required state transformations on the fly. Experimental results on popular server programs (Apache httpd, nginx, OpenSSH and vsftpd ) confirm that our techniques can effectively automate problems previously deemed difficult at the cost of negligible run-time performance overhead (2% on average) and moderate memory overhead (3.9x on average).

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Section: Mutable Tracingmentioning

confidence: 49%

Mutable checkpoint-restart

Giuffrida

Iorgulescu

Tanenbaum

2014

Proceedings of the 15th International Middleware Conference on - Middleware '14

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“…Engineering accurate stack maps is challenging [1,24]. Precise pointer tracking burdens the compiler with significant bookkeeping in optimizations and intermediate representations [21], and inhibits optimizations, such as code motion.…”

Section: Exact Garbage Collectionmentioning

confidence: 99%

“…Exactly identifying root references requires a strict compiler discipline that constructs and maintains stack maps that precisely report every word on the stack and in registers that holds a live reference for every point in execution where a collection may occur. This process is a formidable implementation task that requires tracking every reference in all optimizations and compiler intermediate forms, and it restricts some optimizations, such as code motion [1,21,24].…”

Section: Introductionmentioning

confidence: 99%

Fast conservative garbage collection

Shahriyar

Blackburn

McKinley

2014

Proceedings of the 2014 ACM International Conference on Object Oriented Programming Systems Languages &Amp; Applications

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Garbage collectors are exact or conservative. An exact collector identifies all references precisely and may move referents and update references, whereas a conservative collector treats one or more of stack, register, and heap references as ambiguous. Ambiguous references constrain collectors in two ways.(1) Since they may be pointers, the collectors must retain referents. (2) Since they may be values, the collectors cannot modify them, pinning their referents.We explore conservative collectors for managed languages, with ambiguous stacks and registers. We show that for Java benchmarks they retain and pin remarkably few heap objects: <0.01% are falsely retained and 0.03% are pinned. The larger effect is collector design. Prior conservative collectors (1) use mark-sweep and unnecessarily forgo moving all objects, or (2) use mostly copying and pin entire pages. Compared to generational collection, overheads are substantial: 12% and 45% respectively. We introduce high performance conservative Immix and reference counting (RC). Immix is a mark-region collector with fine linegrain pinning and opportunistic copying of unambiguous referents. Deferred RC simply needs an object map to deliver the first conservative RC. We implement six exact collectors and their conservative counterparts. Conservative Immix and RC come within 2 to 3% of their exact counterparts. In particular, conservative RC Immix is slightly faster than a well-tuned exact generational collector. These findings show that for managed languages, conservative collection is compatible with high performance.

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“…In our experience, however, conservative GC works poorly for long-running programs, such as a web server, a programming environment, or an operating system kernel. For such programs, conservative GC can trigger unbounded memory use due to linked lists [Boehm 2002] that manage threads and continuations; this problem is usually due to liveness imprecision [Hirzel et al 2002], rather than type imprecision. Furthermore, the programs are susceptible to memory-exhaustion attack from malicious code (e.g., user programs or untrusted servlets) that might be otherwise restricted through a sandbox [Wick and Flatt 2004].…”

Section: Gc In Cmentioning

confidence: 99%

“…Second, the collector may assume that a numeric value in the heap is actually a pointer; considered as a pointer, such a number may reference a valid heap location, thus incorrectly marking that location as reachable. For most applications, conservative identification of roots is a more significant problem than misidentification of integers as pointers [Hirzel et al 2002]. Smith and Morrisett [1998] attempted to solve some of the misidentification problems but were still conservative on the stack and other areas of memory.…”

Section: Related Workmentioning

confidence: 99%

Precise garbage collection for C

Rafkind

Wick

Regehr

et al. 2009

Proceedings of the 2009 International Symposium on Memory Management

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Magpie is a source-to-source transformation for C programs that enables precise garbage collection, where precise means that integers are not confused with pointers, and the liveness of a pointer is apparent at the source level. Precise GC is primarily useful for long-running programs and programs that interact with untrusted components. In particular, we have successfully deployed precise GC in the C implementation of a language run-time system that was originally designed to use conservative GC. We also report on our experience in transforming parts of the Linux kernel to use precise GC instead of manual memory management.

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On the usefulness of type and liveness accuracy for garbage collection and leak detection

Cited by 41 publications

References 29 publications

Mutable checkpoint-restart

Mutable checkpoint-restart

Fast conservative garbage collection

Precise garbage collection for C

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