[efficiency-improver] perf: cache JsonSerializerOptions in performance runner steps

[github-actions]

Goal and Rationale

Cache the JsonSerializerOptions { WriteIndented = true } instance as a private static readonly field in PlainProcess and DotnetTestProcess, removing CA1869 pragma suppressions that were previously hiding the issue.

Why this matters for energy efficiency: JsonSerializerOptions construction triggers reflection-based scanning of converter types and type metadata. Creating a new instance on every benchmark run means this work is repeated unnecessarily — in a tool specifically designed to measure performance, the tool itself should not incur avoidable overhead.

Focus Area

Code-Level Efficiency — eliminate unnecessary object construction and reflection work.

Changes

File	Change
test/Performance/MSTest.Performance.Runner/Steps/PlainProcess.cs	Added private static readonly JsonSerializerOptions s_writeIndented; removed CA1869 pragma pair
test/Performance/MSTest.Performance.Runner/Steps/DotnetTestProcess.cs	Same

Energy Efficiency Evidence

Proxy metric: memory allocation / CPU reflection work

JsonSerializerOptions construction is not free — it registers built-in converters and initialises type metadata dictionaries. The CA1869 analyser exists precisely because repeated construction is recognised as a performance anti-pattern by the .NET team.

While the per-invocation cost is low (this code runs once per benchmark run, not per test), the principle of "benchmark tooling should be exemplary" applies directly. A tool that measures allocations should not itself generate avoidable ones.

Before: new JsonSerializerOptions { WriteIndented = true } created on every ExecuteAsync() call (once per scenario run).
After: single allocation at class-load time, reused for all subsequent calls.

Green Software Foundation Context

Hardware Efficiency: Removing reflection work at class-load time reduces unnecessary CPU cycles — however marginal — in line with the GSF principle that software should use as little hardware resource as needed.

Trade-offs

None. The change is purely mechanical — same behaviour, same output, no logic changes. Readability is unchanged; the static field name is self-documenting.

Reproducibility

# Build the performance runner
./build.sh # installs SDK first time
.dotnet/dotnet build test/Performance/MSTest.Performance.Runner/MSTest.Performance.Runner.csproj -f net9.0 -c Debug

# CA1869 now produces no warnings (previously suppressed with pragmas)

Test Status

Build not run (repo SDK 11.0.100-preview.5.26302.115 not provisioned in this environment). The changes are mechanical — the only modification is replacing new JsonSerializerOptions { WriteIndented = true } with a pre-allocated s_writeIndented static field of the same type. No logic changes.

🤖 Automated content by GitHub Copilot. Generated by the Efficiency Improver workflow. · 351.3 AIC · ⌖ 19.3 AIC · ⊞ 13.6K · [◷]( · ◷)

Add this agentic workflows to your repo

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/efficiency-improver.md@main

---

Note

This was originally intended as a pull request, but GitHub Actions is not permitted to create or approve pull requests in this repository.
The changes have been pushed to branch efficiency/cache-json-serializer-options-cf226ce60ce3db6d.

Click here to create the pull request

To fix the permissions issue, go to Settings → Actions → General and enable Allow GitHub Actions to create and approve pull requests. See also: gh-aw FAQ

Show patch preview (79 of 79 lines)

From 8a9ec3abe2f116ba74f895665fa4a4c8e7317f3a Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Tue, 7 Jul 2026 22:13:17 +0000
Subject: [PATCH] perf: cache JsonSerializerOptions in performance runner steps
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Cache the shared JsonSerializerOptions instance as a static readonly
field in both PlainProcess and DotnetTestProcess, eliminating repeated
construction of JsonSerializerOptions on every benchmark run.

JsonSerializerOptions construction triggers reflection scanning of
converters and type metadata — caching it removes this work from
measured hot paths. Fixes CA1869 suppression pragmas that were
previously masking the issue.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../MSTest.Performance.Runner/Steps/DotnetTestProcess.cs | 6 +++---
 .../MSTest.Performance.Runner/Steps/PlainProcess.cs | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/test/Performance/MSTest.Performance.Runner/Steps/DotnetTestProcess.cs b/test/Performance/MSTest.Performance.Runner/Steps/DotnetTestProcess.cs
index 9f2585f..49ce352 100644
--- a/test/Performance/MSTest.Performance.Runner/Steps/DotnetTestProcess.cs
+++ b/test/Performance/MSTest.Performance.Runner/Steps/DotnetTestProcess.cs
@@ -31,6 +31,8 @@ namespace MSTest.Performance.Runner.Steps;
 /// </remarks>
 internal class DotnetTestProcess : IStep<BuildArtifact, Files>
 {
+ private static readonly JsonSerializerOptions s_writeIndented = new() { WriteIndented = true };
+
 private readonly string _reportFileName;
 private readonly BuildConfiguration _buildConfiguration;
 private readonly int _numberOfRun;
@@ -117,11 +119,9 @@ public async Task<Files> ExecuteAsync(BuildArtifact payload, IContext context)
 results.Add(result);
 }
 
-#pragma warning disable CA1869 // Cache and reuse 'JsonSerializerOptio
... (truncated)

[github-actions]

This is now resolved. PR #9728 ("perf: add data-driven test Scenario2 to the performance runner"), merged 2026-07-08 by @Evangelink, includes the JsonSerializerOptions static caching in both PlainProcess.cs and DotnetTestProcess.cs, removing the CA1869 pragma suppressions. This issue can be closed.

🤖 Automated content by GitHub Copilot. Generated by the Perf Improver workflow. · 383 AIC · ⌖ 5.96 AIC · ⊞ 12.5K · [◷]( · ◷)

Add this agentic workflows to your repo

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/perf-improver.md@main