perf: add rendered key byte cache in ByteRenderer - #1118
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Motivation: Object keys are rendered (quoted + escaped) on every materialization. In K8s manifests and similar workloads, the same short keys repeat thousands of times. Each render re-runs getChars + escape scan. Modification: - 64-slot identity-keyed cache for quoted object key bytes - Two-touch pattern: store key on first sight, capture bytes on second identity hit (avoids byte[] allocation for one-shot keys) - Cache hit: System.arraycopy pre-rendered bytes (zero escape scan) - Keys > 32 chars bypass cache entirely (rare, not worth caching) - Identity-keyed (eq) so no hashCode/equals overhead on lookup - Lazy initialization avoids allocation for small outputs Result: MainBenchmark: within noise (no regression). The cache synergizes with identifier interning (databricks#1117) which guarantees stable String identity for field names, maximizing hit rate.
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Motivation
Object keys are rendered (quoted + escaped) on every materialization. In K8s manifests and similar workloads, the same short keys (
apiVersion,kind,metadata,spec) repeat thousands of times across objects. Each render re-runsgetChars+ escape scan unnecessarily.Modification
ByteRendererSystem.arraycopypre-rendered bytes (zero escape scan)key.length <= 32eq) so nohashCode/equalsoverhead on lookupResult
JMH config:
-f 2 -wi 5 -i 10 -w 1 -r 1The
stdlib.jsonnetbenchmark has limited key repetition; the cache's primary benefit is in K8s-style manifests with high key reuse. Synergizes with identifier interning (#1117) which guarantees stable String identity for field names, maximizing cache hit rate.All 424 tests pass.
Test plan
./mill 'sjsonnet.jvm[_]'.test— all pass./mill bench.runJmh ".*MainBenchmark.*"— no regression