perf: use unsynchronized StringBuilderWriter in TomlRenderer#875
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perf: use unsynchronized StringBuilderWriter in TomlRenderer#875He-Pin wants to merge 2 commits into
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Motivation: std.manifestJson* still contributed to the local Scala Native gap versus source-built jrsonnet, especially in real-world object-heavy rendering. Modification: Add an internal StringBuilder-backed FastMaterializeJsonRenderer for std.manifestJson, std.manifestJsonMinified, and std.manifestJsonEx while preserving the public MaterializeJsonRenderer StringWriter API. Reuse an in-place codepoint key sorter backed by java.util.Arrays.sort, and fix raw-surrogate prefix ordering in compareStringsByCodepoint. Result: Full validation passed: ./mill --no-server --ticker false --color false __.reformat and ./mill --no-server --ticker false --color false -j 1 __.test reported 451/451 tests passing. JMH regressions: manifestJsonEx 0.055 ms/op, realistic2 43.596 ms/op, gen_big_object 0.842 ms/op. Direct hyperfine against source-built jrsonnet: manifestJsonEx sjsonnet-native 5.090 ms vs jrsonnet 4.075 ms; kube-prometheus sjsonnet-native 143.738 ms vs jrsonnet 97.385 ms.
std.manifestTomlEx routed through java.io.StringWriter, whose backing StringBuffer pays a monitor enter/exit on every write/flush on the hot TOML manifestation path. Switch TomlRenderer and the manifestTomlEx render path in ManifestModule to the unsynchronized package-private StringBuilderWriter (the same writer the JSON manifest renderer uses). Output is byte-identical; std.deepJoin keeps StringWriter (separate concern). Result (Scala Native hyperfine, TOML-heavy workload, ~1.8 MB output): after ran 1.11 ± 0.07x faster than before (~10%); output byte-identical.
This was referenced May 30, 2026
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Motivation
std.manifestTomlExrouted throughjava.io.StringWriter, whose backingStringBufferpays a monitor enter/exit on everywrite/flushon the hot TOML manifestation path. The JSON manifest renderer already uses the unsynchronizedStringBuilderWriter; TOML did not.Modification
TomlRendererand themanifestTomlExrender path inManifestModulefromjava.io.StringWriterto the package-privateStringBuilderWriter.std.deepJoinkeepsStringWriter(separate concern).Result
Scala Native hyperfine, TOML-heavy workload (~1.8 MB output), interleaved and cooled:
→ 1.14 ± 0.24× faster; output byte-identical.
Test plan
./mill __.reformat./mill 'sjsonnet.jvm[3.3.7]'.test— 518/518 pass