JMH — trustworthy Java microbenchmarks Agent Skill

Write Java microbenchmarks with JMH (Java Microbenchmark Harness) that produce trustworthy numbers — not numbers distorted by JIT…

Context cost
12.6k tokensestimated from the bundle, loaded when it triggers
Bundle
8 files · 50.5 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Write Java microbenchmarks with JMH (Java Microbenchmark Harness) that produce trustworthy numbers — not numbers distorted by JIT dead-code elimination, constant folding, insufficient warmup, or single-fork JIT contamination. Use this skill whenever the user writes `@Benchmark`, mentions JMH, microbenchmark, throughput measurement, latency measurement, or compares two implementations performance-wise.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

javasecuritytesting

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md5.4 kB · preview
--- name: jmh ---
6# JMH — trustworthy Java microbenchmarks
7
8## Workflow
9
101. **Pre-flight before running** — read references/pitfalls.md and apply its 15-point checklist to the benchmark source. Catch DCE, constant folding, missing Blackhole, @Fork(0), @Warmup < 5, final constants in the op, missing @State, raw loops without @OperationsPerInvocation. Most "fast" results come from broken benchmarks; catching this before running saves hours.
112. **Identify the build system** — Maven (pom.xml with jmh-core) or Gradle (me.champeau.jmh plugin). Setup differs; running differs. See references/maven.md or references/gradle.md.
123. **Pick the right Mode** — Throughput for ops/sec, AverageTime for ns/op, SingleShotTime for cold-path / startup, SampleTime for distribution (p50/p99). Wrong mode → wrong question answered. See references/modes.md.
134. **Write the benchmark** — annotate class with @State(Scope.Benchmark), @BenchmarkMode, @OutputTimeUnit, @Fork(value=3, jvmArgs={"-Xmx2g","-Xms2g"}), @Warmup(iterations=5), @Measurement(iterations=10). Every @Benchmark method either returns a value or takes a Blackhole parameter. Use @Param for matrices instead of separate methods.
145. **Re-check the source against the checklist** after edits.
156. **Run with profilers attached** — never run benchmarks without -prof gc (allocation rate context) and ideally -prof async:output=flamegraph (flame graph per benchmark). See references/profilers.md.
167. **Output JSON** (-rf json -rff results.json) — never trust the console table alone; JSON is what diffing and visualization tools consume.
178. **Analyze** — drag results.json to https://jmh.morethan.io for charts, or use Bencher/Codspeed in CI for continuous diff. See references/analysis.md.
189. **Report with confidence intervals** — JMH prints Score ± Error (99.9%). Two means are *not* different if their confidence intervals overlap. Don't claim "10% faster" inside the noise band.
19
20## Quick reference
21
22```bash
23# Maven — build + run a single benchmark class
24mvn clean verify -DskipTests
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md709 words
Files8
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈280
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
12,345
on trigger
The instruction body and 7 supporting files, read only when the skill fires.
6.3%
of a 200k window
Ten skills this size would take about 63% of the window before you open a file.
050k100k150k200k context window

12.6k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

8 files, 50.5 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md5.4 kB
  • references/analysis.md5.3 kB
  • references/gradle.md5.8 kB
  • references/intro.md9.3 kB
  • references/maven.md5.0 kB
  • references/modes.md5.7 kB
  • references/pitfalls.md8.6 kB
  • references/profilers.md5.4 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 8 files you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# JMH — trustworthy Java microbenchmarks · 12.6k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/jmh-trustworthy-java-microbenchmarks/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/jmh-trustworthy-java-microbenchmarks" ] && { [ ! -e .claude/skills/jmh-trustworthy-java-microbenchmarks ] || { mv .claude/skills/jmh-trustworthy-java-microbenchmarks "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/jmh-trustworthy-java-microbenchmarks" .claude/skills/ && echo "Installed .claude/skills/jmh-trustworthy-java-microbenchmarks"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add thanhbinhbent/jmh-trustworthy-java-microbenchmarks

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/jmh-trustworthy-java-microbenchmarks/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/jmh-trustworthy-java-microbenchmarks/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/jmh-trustworthy-java-microbenchmarks" ] && { [ ! -e ~/.claude/skills/jmh-trustworthy-java-microbenchmarks ] || { mv ~/.claude/skills/jmh-trustworthy-java-microbenchmarks "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/jmh-trustworthy-java-microbenchmarks" ~/.claude/skills/ && echo "Installed ~/.claude/skills/jmh-trustworthy-java-microbenchmarks" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/jmh-trustworthy-java-microbenchmarks/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as jmh in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, jmh-trustworthy-java-microbenchmarks.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referencethanhbinhbent/jmh-trustworthy-java-microbenchmarks

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

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