tracing-log: Use a faster interest-cache hasher #3356
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hoxxep
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Aug 4, 2025
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hoxxep
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tracing-log/Cargo.toml
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| [dev-dependencies] | ||
| tracing = { path = "../tracing", version = "0.1.35"} | ||
| tracing-subscriber = { path = "../tracing-subscriber" } | ||
| criterion = { version = "0.3.6", default-features = false } | ||
| tracing-subscriber = { path = "../tracing-subscriber", features = ["env-filter"] } |
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I can't tell if this feature here is breaking the build. It's required to run the benchmarks, but will remove from the commit.
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Motivation
ahash benchmarks to 13ns on
log_from_multiple_threadsrapidhash benchmarks to 9ns on
log_from_multiple_threadsSolution
I've recently released rapidhash v3.0 which is faster than ahash on every platform I have benchmarked, especially for hashing integer pairs and shorter strings. There are benchmarks for u64 pairs detailed on various server platforms in the docs folder of the repo to demonstrate a consistent ~35% improvement of hashing integer pairs over ahash.
This MR significantly improves the performance of the interest cache by changing the LRU cache hasher to rapidhash. Rapidhash has a high quality hash output (passes the SMHasher3 hash benchmarks), is cross-platform, and minimally DoS resistant, so I don't believe there is a drawback to switching? I appreciate I'm biased though!