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Visualising Dynamic Memory Allocators

Andrew Cheadle, A. J. Field, J.W. Ayres, N. Dunn, Richard Hayden, J. Nystrom-Persson

Conference or Workshop Paper
ISMM'06, ACM International Symposium on Memory Management
May, 2006
ACM Press
ISBN 1-59593-221-6
DOI 10.1145/1133956.1133972

We present generic extensions to the GCspy visualisation framework that make it suitable for tracking the way continuous dynamic memory allocators such as dlmalloc or incremental and concurrent garbage collectors make use of heap memory.

These extensions include sample-driven client-server communication, incremental stream updates and client-controlled stream update frequency. Additional extensions to the current GCspy client are also described. These include hierarchical driver grouping and hierarchical visualisation, zooming, and the ability to define and view relationships between tiles in different spaces. We also introduce a heuristics engine that is responsible for flipping GCspy from its decoupled 'observation' mode to a synchronous 'single-step' mode, and describe a backtrace facility that can trace the server-side call sequence that led to the triggering of a specified event, such as the allocation or freeing of a block of memory.

This enables aspects of the allocator (fragmentation, block ordering, splitting and coalescing policies, etc.) to be understood in the context of a particular application and potential optimisations to be identified. The effectiveness of the enhanced framework is demonstrated with a complete integration with dlmalloc. The framework is evaluated in terms of both performance and its ability to explore contrived modifications to dlmalloc's coalescing policy.

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