perf: optimize classic-only histogram observe path#2252
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Signed-off-by: Arnab Nandy <arnab_nandy7@yahoo.com>
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Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
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Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
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## Summary Extract the PR benchmark workflows from #2252 into a standalone PR so they can land on `main` first. ## Why The benchmark job uploads a Markdown artifact with the PR comment contents, but the actual PR comment is posted by a separate `workflow_run` workflow. GitHub only triggers `workflow_run` workflows when the workflow file already exists on the default branch, so keeping the reporter in the same PR prevents it from commenting on that PR's benchmark run. Splitting these workflows out first lets subsequent benchmark PRs use the comment-reporting flow as intended. ## Changes - add `PR Benchmarks` workflow triggered by the `benchmark` label on pull requests - add `PR Benchmark Report` workflow triggered by `workflow_run` - keep the benchmark summary as an uploaded artifact consumed by the reporter workflow ## Testing - `mise run lint:fix`
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## Summary The `PR Benchmark Report` workflow failed to comment on [#2252](#2252) after a successful benchmark run ([run 28865892835](https://github.com/prometheus/client_java/actions/runs/28865892835)): ``` gh: Not Found (HTTP 404) parse "https://api.github.com/repos/prometheus/client_java/issues/comments/{\r": net/url: invalid control character in URL ``` Root cause: `workflow_run.pull_requests` is empty when the triggering run's head branch is not on the default branch (or the PR is from a fork). With `PR_NUMBER` empty, the subsequent `repos/${REPO}/issues//comments` API call 404s and the paginator emits a malformed URL, so no comment gets posted. ## Changes - Fall back to `repos/{owner}/{repo}/commits/{sha}/pulls` to resolve the PR from the head SHA when `workflow_run.pull_requests` is empty. - Fail fast with an explicit error if the PR still can't be resolved, so future regressions don't cascade into cryptic URL-parse errors. ## Test plan - [ ] Re-run the report workflow against run 28861406560 (or a fresh push to #2252) and confirm a benchmark comment lands on the PR. Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
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Jul 9, 2026
## Summary Fix the `PR Benchmark Report` workflow for forked PR benchmark runs like #2252, where `workflow_run.pull_requests` and `commits/{sha}/pulls` can both be empty for the upstream repository. ## Changes - Resolve the PR number from the uploaded benchmark artifact names first. - Fall back to the workflow run head repository owner and branch via `repos/{owner}/{repo}/pulls`. - Keep the existing commit-SHA lookup as a final fallback. - Remove the artifact ZIP download `Accept: application/octet-stream` header because `gh api` rejected it during local replay. ## Validation - Replayed the resolution logic against benchmark run `28928458470` and confirmed it resolves PR #2252 and downloads artifact `8164318312`. - Ran `mise run lint:fix`. - Ran `git diff --check`.
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Benchmark resultsBenchmark run succeeded for
Prometheus Java Client BenchmarksRun Information
Comparison with base
Results for PR headCounterBenchmark
HistogramBenchmark
HistogramTextFormatBenchmark
TextFormatUtilBenchmark
Raw ResultsNotes
Benchmark Descriptions
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## Summary Make PR benchmark comments answer whether the PR is faster or slower than its base commit, while keeping wall-clock time close to a single benchmark run. ## Changes - Run base and head benchmarks in parallel matrix jobs. - Add a lightweight summary job that downloads both raw JMH artifacts and generates the PR comment. - Add a `Comparison with base` table to the generated `README.md` / PR comment. - Mark each benchmark as `faster`, `slower`, or `within noise` using JMH confidence intervals when available. - Capture and show runner hardware for both base and head jobs, including a note that parallel jobs may run on different hardware. - Rename the existing per-run relative column to `Within run` so it is clear that it is not the base comparison. - Store `baseline-results.json` in the uploaded benchmark artifact for inspection. ## Validation - Ran `mise run lint:fix`. - Ran `python3 -m py_compile .mise/tasks/generate_benchmark_summary.py`. - Ran `git diff --check`. - Replayed summary generation with the latest #2252 benchmark artifact and the published benchmark baseline; the output now shows `HistogramBenchmark.prometheusClassic` as `-78.6%` / `slower`. - Verified no-baseline summary generation still omits the comparison section. ## Tradeoff Parallel base/head jobs are faster wall-clock than measuring both commits sequentially on one runner, but runner hardware can differ. The comment now prints both runner descriptions and calls out that caveat.
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the bench is not comparing to main - I'll fix that |
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## Summary Replace the parallel base/head PR benchmark comparison with topic-split benchmark jobs. Each topic compares base and head sequentially on the same runner, while topics still run in parallel for better wall-clock time. ## Changes - Split PR benchmarks into topic jobs: counter, histogram, and exposition. - Run base and head sequentially inside each topic job so each comparison uses the same runner. - Merge per-topic JMH JSON results in the summary job before generating the PR comment. - Add a comparison note clarifying that base/head are compared on the same runner within each topic. - Add histogram benchmark variants for classic-only histograms: - shared contended 4-thread benchmark remains as `prometheusClassic` - single-thread benchmark: `prometheusClassicSingleThread` - per-thread 4-thread benchmark: `prometheusClassicPerThread` ## Why Running base and head in separate jobs was faster but not reliable enough because GitHub Actions can schedule them on different CPU models. Topic splitting keeps the reliable same-runner comparison within each topic while still allowing unrelated benchmark topics to run in parallel. ## Validation - Ran `mise run lint:fix`. - Ran `mise run build`. - Ran `python3 -m py_compile .mise/tasks/generate_benchmark_summary.py`. - Ran `git diff --check`. - Verified the JMH include patterns select the intended benchmarks with `java -jar benchmarks/target/benchmarks.jar -l ...`. - Smoke-tested the topic result merge and summary generation using the latest #2252 benchmark artifact.
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Summary
Optimizes
Histogram.classicOnly()observations by adding a dedicated classic-only fast path that uses synchronized plain fields instead of the native/hybridLongAdder/DoubleAdderplus buffer path.Fixes #1915
Changes
Histogram.DataPoint.observe()andobserveWithExemplar()through the classic-only fast path whennativeInitialSchema == CLASSIC_HISTOGRAM.Testing
.\mvnw compile -pl prometheus-metrics-core -Dcoverage.skip=true -Dcheckstyle.skip=truegit diff --check