Add a threading-correct TagMap access microbenchmark

[dougqh]

What

Adds a throughput microbenchmark for the core TagMap access paths — insert, getObject (raw value), getEntry — over a representative HTTP-server-ish tag set.

Threading correctness

Runs at @Threads(8). All shared state is immutable (NAMES/VALUES); every bit of mutable state (the pre-populated read map) lives in a @State(Scope.Thread) holder, so threads never contend on a shared map, index, or reader flyweight. Earlier TagMap benchmarks shared a cross-thread counter/index, which turned the result into a contention measurement rather than a TagMap measurement — this layout avoids that. Indices are plain per-invocation locals.

Run config is baked into annotations (@Fork/@Warmup/@Measurement/@Threads) rather than relying on -Pjmh.* flags, which the me.champeau.jmh plugin ignores.

Notes

• Independent of the LegacyTagMap removal (Remove LegacyTagMap; OptimizedTagMap is the sole TagMap implementation #11678) — uses only the public TagMap API, so it builds/runs on master and on that branch alike.
• First of a planned per-span-type benchmark suite (web/db/queue/…), which gives instrumentation authors relatable numbers and is the natural vehicle for demonstrating per-type optimizations later. The per-type DDSpan benchmark follows once its tracer setup is quieted (a no-op writer to stop per-op DEBUG logging from contaminating throughput).

🤖 Generated with Claude Code

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⚠️ Warnings

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DataDog/apm-reliability/dd-trace-java | linux-java-spring-petclinic-sca-load-parallel     

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[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	14.00 s	13.90 s	[+0.1%; +1.4%] (maybe worse)
startup:insecure-bank:tracing:Agent	12.86 s	12.98 s	[-1.9%; -0.0%] (maybe better)
startup:petclinic:appsec:Agent	16.44 s	16.53 s	[-4.8%; +3.8%] (no difference)
startup:petclinic:iast:Agent	16.76 s	16.81 s	[-1.4%; +0.9%] (no difference)
startup:petclinic:profiling:Agent	16.23 s	16.41 s	[-7.1%; +4.9%] (unstable)
startup:petclinic:sca:Agent	16.85 s	16.64 s	[+0.2%; +2.2%] (maybe worse)
startup:petclinic:tracing:Agent	15.93 s	15.60 s	[-2.0%; +6.3%] (no difference)

Commit: 94830b2f · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.