bench: calibrate new ssr benchmarks iteration to reduce variability

[Sheraff]

increase iteration count in new SSR benchmarks for all those that were running in under 50ms. The goal is to improve the signal to noise ratio, and reduce variability in the results.

I'm not sure this is the solution, but I also think it can't hurt. CodSpeed has been very stable for us so far.

---

Also, improve response drain, from response.text() to a .getReader() that ignores all chunks.

Summary by CodeRabbit

• Tests
  • Standardized and increased iteration counts across multiple SSR benchmark scenarios for more consistent measurements.
  • Split shared loop settings into per-scenario iteration controls.
  • Switched benchmark validation to operate on full responses and added a helper to consume response streams asynchronously for more reliable benchmarking.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 3bb0af71-3aea-49c7-86ca-983fd3a7a912

📥 Commits

Reviewing files that changed from the base of the PR and between ddbbc64 and 7def91e.

📒 Files selected for processing (2)

• benchmarks/ssr/scenarios/assets/shared.ts
• benchmarks/ssr/scenarios/serialization/shared-bench.ts

✅ Files skipped from review due to trivial changes (1)

• benchmarks/ssr/scenarios/assets/shared.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• benchmarks/ssr/scenarios/serialization/shared-bench.ts

---

📝 Walkthrough

Walkthrough

This PR centralizes and increases per-scenario benchmark iteration counts across SSR scenarios, replaces shared loop option objects with per-scenario constants, and changes bench-utils to validate using the Response and asynchronously drain response bodies.

Changes

Benchmark Iteration Parameterization

Layer / File(s)	Summary
Simple iteration constant adjustments benchmarks/ssr/scenarios/before-load/shared-bench.ts, benchmarks/ssr/scenarios/control-flow/shared.ts, benchmarks/ssr/scenarios/server-routes-middleware/shared.ts, benchmarks/ssr/scenarios/server-routes/shared.ts	Direct updates to existing iteration constants: before-load from 20→30, control-flow constants increased (to 45/50/60), server-routes-middleware 100→150, server-routes 100→200.
New iteration constants with single-runner wiring benchmarks/ssr/scenarios/assets/shared.ts, benchmarks/ssr/scenarios/head/shared.ts, benchmarks/ssr/scenarios/loaders/shared-bench.ts, benchmarks/ssr/scenarios/rewrites/shared.ts, benchmarks/ssr/scenarios/selective-ssr/shared-bench.ts, benchmarks/ssr/scenarios/serialization/shared-bench.ts	Introduce dedicated iteration constants (e.g., inlineCssLoopIterations, headLoopIterations, loadersLoopIterations, localizedLoopIterations, passthroughLoopIterations, selectiveLoopIterations, richSerializationLoopIterations) and wire them into individual run*Loop calls.
Complex multi-scenario iteration refactoring & bench-utils changes benchmarks/ssr/scenarios/global-middleware/bench.ts, benchmarks/ssr/scenarios/server-fn-transport/bench.ts, benchmarks/ssr/scenarios/server-fns/bench.ts, benchmarks/ssr/bench-utils.ts	Replace shared request-loop options with per-scenario iteration constants (multiple new constants per file). bench-utils.ts adds drainResponse, replaces validateBody with validateResponse, and switches loops to asynchronously drain responses.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• TanStack/router#7606: Modifies runRequestLoop options and response consumption in benchmarks/ssr/bench-utils.ts, similar to this PR.

Suggested reviewers

• schiller-manuel

🐰 Iterations named and tidy, streams drained with care,
Benchmarks march onward, numbers counted fair,
Constants lined like carrots, neat in every row,
A rabbit hops in joy — steady metrics, steady flow!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: calibrating SSR benchmark iterations to reduce variability by increasing iteration counts for fast-completing benchmarks.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch perf-ssr-calibrate-iterations

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[nx-cloud]

View your CI Pipeline Execution ↗ for commit 7def91e

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---

☁️ Nx Cloud last updated this comment at 2026-06-13 09:34:34 UTC

[github-actions]

🚀 Changeset Version Preview

3 package(s) bumped directly, 10 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
@tanstack/react-router	1.170.15 → 1.170.16	Changeset
@tanstack/solid-router	1.170.15 → 1.170.16	Changeset
@tanstack/start-server-core	1.169.14 → 1.169.15	Changeset
@tanstack/react-start	1.168.25 → 1.168.26	Dependent
@tanstack/react-start-client	1.168.13 → 1.168.14	Dependent
@tanstack/react-start-rsc	0.1.24 → 0.1.25	Dependent
@tanstack/react-start-server	1.167.19 → 1.167.20	Dependent
@tanstack/solid-start	1.168.25 → 1.168.26	Dependent
@tanstack/solid-start-client	1.168.13 → 1.168.14	Dependent
@tanstack/solid-start-server	1.167.19 → 1.167.20	Dependent
@tanstack/start-plugin-core	1.171.17 → 1.171.18	Dependent
@tanstack/vue-start	1.168.24 → 1.168.25	Dependent
@tanstack/vue-start-server	1.167.19 → 1.167.20	Dependent

[github-actions]

Bundle Size Benchmarks

• Commit: 26030114eca0
• Measured at: 2026-06-13T09:31:22.565Z
• Baseline source: history:a2b9d51b0a21
• Dashboard: bundle-size history

Scenario	Current (gzip)	Delta vs baseline	Initial gzip	Raw	Brotli	Trend
react-router.minimal	87.29 KiB	0 B (0.00%)	87.15 KiB	273.66 KiB	75.88 KiB	▁▁▁▁▁▁▃████
react-router.full	91.02 KiB	0 B (0.00%)	90.88 KiB	285.56 KiB	79.09 KiB	███▁▁▁▁▄▄▄▄
solid-router.minimal	35.48 KiB	0 B (0.00%)	35.36 KiB	105.86 KiB	32.03 KiB	▆▆▆▆█▁▁▁▁▁▁
solid-router.full	40.53 KiB	0 B (0.00%)	40.41 KiB	121.08 KiB	36.46 KiB	▆▆▆▆█▁▁▁▁▁▁
vue-router.minimal	52.97 KiB	0 B (0.00%)	52.84 KiB	149.90 KiB	47.62 KiB	████▁▁▁▁▁▁▁
vue-router.full	58.96 KiB	0 B (0.00%)	58.83 KiB	168.66 KiB	52.87 KiB	▁▁▁▁███████
react-start.minimal	101.91 KiB	0 B (0.00%)	101.77 KiB	321.98 KiB	88.21 KiB	▁▁▁▁▂▂▃████
react-start.deferred-hydration	102.65 KiB	0 B (0.00%)	101.80 KiB	323.36 KiB	88.90 KiB	▁▁▁▂▂▂▂████
react-start.full	105.31 KiB	0 B (0.00%)	105.18 KiB	331.91 KiB	91.06 KiB	███▁▁▁▂▆▆▆▆
react-start.rsbuild.minimal	99.63 KiB	0 B (0.00%)	99.46 KiB	316.43 KiB	85.79 KiB	▃▃▃▁▂▂▃████
react-start.rsbuild.minimal-iife	100.03 KiB	0 B (0.00%)	99.87 KiB	317.37 KiB	86.08 KiB	▃▃▃▁▂▂▃████
react-start.rsbuild.full	102.86 KiB	0 B (0.00%)	102.68 KiB	326.48 KiB	88.53 KiB	███▁▁▁▁▅▅▅▅
solid-start.minimal	49.60 KiB	0 B (0.00%)	49.47 KiB	151.93 KiB	43.79 KiB	▆▆▆▆█▁▁▁▁▁▁
solid-start.deferred-hydration	52.86 KiB	0 B (0.00%)	49.53 KiB	159.97 KiB	46.81 KiB	▄▄▄▄█▁▁▁▁▁▁
solid-start.full	55.40 KiB	0 B (0.00%)	55.27 KiB	168.97 KiB	48.80 KiB	▅▅▅▅█▁▁▁▁▁▁
vue-start.minimal	71.02 KiB	0 B (0.00%)	70.89 KiB	207.04 KiB	62.93 KiB	▁▁▁▁███████
vue-start.full	75.01 KiB	0 B (0.00%)	74.88 KiB	219.68 KiB	66.40 KiB	▁▁▁▁███████

Current gzip tracks all emitted client JS chunks. Initial gzip tracks only the entry/import graph. Trend sparkline is historical current gzip ending with this PR measurement; lower is better.

[pkg-pr-new]

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commit: 7def91e

[codspeed-hq]

Merging this PR will degrade performance by 45.01%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 3 improved benchmarks
❌ 78 (👁 78) regressed benchmarks
✅ 15 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	ssr server-fn raw-stream (react)	125 ms	106.4 ms	+17.46%
⚡	Simulation	ssr server-fn raw-stream (solid)	130.7 ms	111.7 ms	+17%
⚡	Simulation	ssr server-fn raw-stream (vue)	128.4 ms	110.5 ms	+16.26%
👁	Simulation	ssr not-found (vue)	73.3 ms	168.8 ms	-56.57%
👁	Simulation	ssr head (vue)	147 ms	324.9 ms	-54.75%
👁	Simulation	ssr loaders (vue)	94.4 ms	136.7 ms	-30.94%
👁	Simulation	ssr selective (vue)	72 ms	139.8 ms	-48.48%
👁	Simulation	ssr server-fn POST (vue)	49.6 ms	71.4 ms	-30.43%
👁	Simulation	ssr server-route middleware (vue)	44.8 ms	63.2 ms	-29.25%
👁	Simulation	ssr server-route (vue)	33.6 ms	60.7 ms	-44.56%
👁	Simulation	ssr assets inline-css cdn (vue)	82.3 ms	187.6 ms	-56.1%
👁	Simulation	ssr assets linked-css control (vue)	72 ms	214.5 ms	-66.43%
👁	Simulation	ssr before-load chain (vue)	127.3 ms	183.8 ms	-30.72%
👁	Simulation	ssr control-flow error 500 (vue)	92.9 ms	198.1 ms	-53.13%
👁	Simulation	ssr control-flow route headers (vue)	88.6 ms	213.4 ms	-58.51%
👁	Simulation	ssr control-flow unmatched 404 (vue)	128.5 ms	190.1 ms	-32.39%
👁	Simulation	ssr global-mw document (vue)	92.4 ms	221 ms	-58.18%
👁	Simulation	ssr global-mw server-fn (vue)	48.8 ms	59.9 ms	-18.65%
👁	Simulation	ssr global-mw server-route (vue)	29.6 ms	71.6 ms	-58.6%
👁	Simulation	ssr rewrite localized (vue)	80.1 ms	177.3 ms	-54.85%
...	...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing perf-ssr-calibrate-iterations (7def91e) with main (a2b9d51)}