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35 lines
1.8 KiB
Markdown
35 lines
1.8 KiB
Markdown
# Benchmarks
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- [`mt-gcbench.c`](./mt-gcbench.c): The multi-threaded [GCBench
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benchmark](https://hboehm.info/gc/gc_bench.html). An old but
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standard benchmark that allocates different sizes of binary trees.
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As parameters it takes a heap multiplier and a number of mutator
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threads. We analytically compute the peak amount of live data and
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then size the GC heap as a multiplier of that size. It has a peak
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heap consumption of 10 MB or so per mutator thread: not very large.
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At a 2x heap multiplier, it causes about 30 collections for the `mmc`
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collector, and runs somewhere around 200-400 milliseconds in
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single-threaded mode, on the machines I have in 2022. For low thread
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counts, the GCBench benchmark is small; but then again many Guile
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processes also are quite short-lived, so perhaps it is useful to
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ensure that small heaps remain lightweight.
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To stress `mmc`'s handling of fragmentation, we modified this
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benchmark to intersperse pseudorandomly-sized holes between tree
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nodes.
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- [`quads.c`](./quads.c): A synthetic benchmark that allocates quad
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trees. The mutator begins by allocating one long-lived tree of depth
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N, and then allocates 13% of the heap in depth-3 trees, 20 times,
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simulating a fixed working set and otherwise an allocation-heavy
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workload. By observing the times to allocate 13% of the heap in
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garbage we can infer mutator overheads, and also note the variance
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for the cycles in which GC hits.
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## License
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mt-gcbench.c was originally from https://hboehm.info/gc/gc_bench/, which
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has a somewhat unclear license. I have modified GCBench significantly
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so that I can slot in different GC implementations. Other files are
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distributed under the Whippet license; see the top-level
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[README.md](../README.md) for more.
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