perf: speed up manifest JSON rendering#874
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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.
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Motivation: The JVM/char render hot path (BaseCharRenderer.visitNonNullString) ran a CharSWAR.hasEscapeChar scan on every string, even for Val.AsciiSafeStr which is statically known to need no JSON escaping (chars 0x20-0x7e, no quote/backslash). The Native ByteRenderer already had this bypass; the char path did not. Modification: - Add BaseCharRenderer.visitAsciiSafeString: quote + bulk getChars + quote, correct even under escapeUnicode since all chars are <= 0x7e. - Route Val.AsciiSafeStr through it via a Materializer.visitStr helper at the three value-string sites; ujson.Value AST path falls back to visitString. - Add AsciiSafeRenderBenchmark to isolate the render path for A/B. Result: JMH render-only, 335KB string-heavy output: 1.606 -> 1.441 ms/op (-10.3%, non-overlapping error bands). 450/450 tests pass.
Motivation: 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. The JSON renderer already switched to the unsynchronized StringBuilderWriter in databricks#874 (-9.3% on kube-prometheus native); TOML did not. Modification: - Switch TomlRenderer and the manifestTomlEx render path in ManifestModule from java.io.StringWriter to the package-private StringBuilderWriter. Output is byte-identical. std.deepJoin keeps StringWriter (separate concern). - Add TomlRenderBenchmark to A/B the render path. Result: Native hyperfine, TOML-heavy workload (1.79MB output): after ran 1.11 ± 0.07x faster than before (~10%), output byte-identical. JMH (whole-pipeline) showed AFTER < BEFORE in two independent rounds. 450/450 tests pass.
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Motivation
std.manifestJson,std.manifestJsonMinified, andstd.manifestJsonExstill routed throughStringWriter, payingStringBuffersynchronization perwriteand perflushon the hot manifestation path. Source-built jrsonnet comparisons showed sjsonnet trailing on object-heavy manifest workloads.Modification
StringBuilderWriter: an unsynchronizedWriterover aStringBuilder.FastMaterializeJsonRendererbacked byStringBuilderWriter; route the threestd.manifestJson*builtins through it. PublicMaterializeJsonRendererABI/shape unchanged.UnicodeHandlingTestsextended for the prefix-ordering case.Result
Scala Native hyperfine on kube-prometheus,
-N -w 4 -m 20, jrsonnet HEAD2d7eed05:manifestJsonEx, sjsonnetmanifestJsonEx, jrsonnetJMH regression post-PR:
manifestJsonEx0.055 ms/op,realistic243.6 ms/op,gen_big_object0.842 ms/op.Related: #666.
Test plan
./mill __.reformat./mill -j 1 __.test— 450/450 pass