[perf-improver] Monthly Activity 2026-08

[github-actions]

Activity for August 2026

Suggested Actions for Maintainer

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Performance Opportunities Backlog

• PrivateObject.Helpers.cs BuildGenericMethodCacheForType: rebuilds cache per instance (net-framework-only path), not shared across instances of same type. Medium risk, low priority - not fixed.
• TestExecutionManager.ParallelExecution.cs: wraps each test element into a new array per test for scheduling; inherent to chunking design, medium risk/effort - not fixed.
• Microsoft.Testing.Platform/Configurations/AggregatedConfiguration.cs: linear provider scan per lookup; low impact, not fixed.
• ServerTestHost.RequestExecution.cs: .Select().ToArray() on testNodes, once per run request (not per-test) - low priority, not fixed.
• RetryArtifactProcessor.cs: GroupBy/Any(Count()) double-enumeration, only matters with many retries+artifacts (low volume) - not fixed.

Codebase remains thoroughly optimized after many scan passes; most prior findings have been fixed and merged (see Run History).

Discovered Commands

./build.sh # restore + build (Debug)
./build.sh -test # build + unit tests
./build.sh -pack # produce NuGet packages
./build.sh -pack -test -integrationTest # full suite (slow)
# SDK bootstrapped via ./build.sh into .dotnet/
# Note: MSTestAdapter.UnitTests and other net48-targeting tests can't run on Linux (no .NET Framework SDK)

Run History

2026-08-31 13:37 UTC - Run

• 🔍 Task 2: explore-agent scan of MSTestAdapter.PlatformServices/Services, remaining StringAssert/CollectionAssert internals, Telemetry (remaining files), TestHost/Hosts per-test-node dispatch, Framework invocation loop, Discovery (AssemblyEnumerator/TypeEnumerator) - all confirmed cold/startup/failure-path or already optimized; no new hot-path findings
• 📊 Task 4: no open PRs with "[perf-improver]" title prefix (checked open PRs list)
• 📊 Task 5: no open performance-labeled issues found (search_issues 0 results)
• 📊 Noted PR Add benchmarks for data source display names #10889 "Add benchmarks for data source display names" (maintainer's own PR, continuing prior perf-improver benchmark work from Add reproducible MSTest performance benchmarks #10843) is open with green state/needs-review label - not perf-improver's own PR, no action needed

2026-08-30 13:33 UTC - Run

• 📊 Confirmed prior draft PR "Add benchmark coverage for TestDataSourceUtilities display-name computation" merged as Add reproducible MSTest performance benchmarks #10843 ("Add reproducible MSTest performance benchmarks")
• 🔍 Task 2: explore-agent scan of TestMethodAttributes/Execution path, Discovery, Platform/Framework invocation, non-terminal OutputDevices, MessageBus, Assertions (ThrowsExactlyAsync/CollectionAssert) - all confirmed already optimized; no new hot-path findings
• 📊 No open perf-improver PRs or performance-labeled issues this run

2026-08-29 13:31 UTC - Run

• 🔍 Task 6: assessed measurement infra - TestDataSourceUtilities.ComputeDefaultDisplayName had no dedicated benchmark
• 🔧 Created draft PR: "Add benchmark coverage for TestDataSourceUtilities display-name computation" (branch perf-assist/testdatasource-benchmark)
• 📊 Verified: ./build.sh -c Release succeeded; ran new benchmark (short job) - 448.5ns/768B and 437.8ns/792B

2026-08-28 17:31 UTC - Run

• 🔍 Scanned Platform Services/Helpers/Capabilities, Adapter reflection, remaining Assert helpers, Analyzers Helpers - no new hot-path findings

2026-08-27 - Run

• 🔍 Scanned HtmlReport/AzureDevOpsReport, CrashDump/HangDump, Configurations, Logging, Assertions, Adapter Execution - no new findings

2026-08-26 - Run

• 🔍 Scanned PlatformServices reflection helpers, Hosts, CommandLine, Requests, MSTest.Sdk, Analyzers codefixes - no new findings

2026-08-25 - Run

• 🔍 Scanned PlatformServices Utilities, Hosts, Requests, Assertions, Retry, MSBuild extension - minor low-priority items noted (ServerTestHost Select+ToArray, RetryArtifactProcessor GroupBy/Count)

2026-08-24 - Run

• 🔍 Scanned Adapter ObjectModel/Utilities, PlatformServices Services/Utilities, TestHost/Requests, TrxReportEngine, Assertions - no new findings

2026-08-23 - Run

• 🔍 Scanned Extensions/ArtifactPostProcessing, Helpers, OutputDevice/Terminal, SourceGeneratedReflectionOperations, CollectionAssert, Adapter reflection - no new findings
• 📌 Noted maintainer PR Reduce ServerMode notification allocations #10670 "Reduce ServerMode notification allocations" continuing prior perf-improver work

2026-08-22 - Run

• 🔍 Identified opportunity: LINQ Select+ToList(object) / Where in ServerMode TestNodeSerializers/TestNodeStateChangeAggregator per-notification hot path
• 🔧 Created PR: "Avoid LINQ allocations on ServerMode per-notification hot path" (branch perf-assist/testnode-changes-serialize-loop)
• 📊 Measured: 8-item array, 2M iters - 447ms/320.4MB alloc -> 205ms/228.9MB alloc (~54% faster, ~29% less alloc)

2026-08-21 - Run

• 🔍 Scanned Retry, MSBuild, HotReload, Telemetry, TestFramework.Extensions - confirmed clean, one false-positive investigated and ruled out

2026-08-20 - Run

• 🔍 Scanned Assert success-paths, OutputDeviceManager, TestResultMessagesSerializer, ReflectionOperations, TreeNodeFilter - no new findings

2026-08-19 - Run

• 🔍 Scanned IPC, TRX/CTRF/JUnit writers, MSTest.TestAdapter, Assert.cs core - confirmed already well-optimized

2026-08-18 - Run

• 📊 PRs Reduce assertion telemetry contention #10560, Optimize non-generic collection count assertions #10575, Optimize VSTestBridge property lookup #10586 all MERGED by maintainer - three perf-improver-originated optimizations landed
• 🔍 Scanned Discovery pipeline, Capabilities, DataRow/DynamicData, Analyzers, PlatformServices - minor low-impact notes only

2026-08-16 - Run

• 🔍 Scanned Adapter Execution, Platform Hosting/Extensions, Configurations, CollectionAssert/StringAssert - no significant new findings

2026-08-15 - Run

• 🔍 Scanned PlatformServices/Services, Assertions, Platform Requests/Messages, Logging - no new findings

2026-08-14 - Run

• 🔄 Reviewed open PRs Reduce assertion telemetry contention #10560, Optimize non-generic collection count assertions #10575, Optimize VSTestBridge property lookup #10586 (maintainer continuing perf-improver work) - all green CI, awaiting review> 🤖 Automated content by GitHub Copilot. Generated by the Perf Improver workflow. · auto · 100.9 AIC · ⌖ 2.45 AIC · ⊞ 18.7K · [◷]( · ◷)

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---

Closing out August 2026 activity — continued in the September 2026 Monthly Activity issue.> 🤖 Automated content by GitHub Copilot. Generated by the Perf Improver workflow. · auto · 84.4 AIC · ⌖ 2.2 AIC · ⊞ 18.7K · [◷]( · ◷)

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[Evangelink]

The remaining perf-improver backlog items are handled in #10384:

• DotnetTestHttpClient new byte[1] trailing-byte probe -> reuses one instance-wide buffer (requests are serialized by _requestLock).
• SilenceDrivenHeartbeatRenderer.BuildSlowTestDescription -> reuses a single StringBuilder, same single-rendering-thread ownership as the backoff dictionary next to it.
• AnsiTerminal.StopUpdate() -> unblocked. IConsole gained a Write(StringBuilder) overload that SystemConsole forwards to TextWriter.Write(StringBuilder) on .NET, so the multi-KB batched progress block is no longer copied into a fresh string on every refresh tick. netstandard2.0 / .NET Framework keep the ToString() copy behind an #if, so nothing regresses there.
• OpenTelemetryResultHandler.GetFullyQualifiedName() -> intentionally left alone. It is one logical string build per test result on the OTel-only path; string.Concat with 5 operands, string.Join and a StringBuilder are all neutral-or-worse than what the compiler already emits for the interpolation. Dropping it from the backlog rather than churning the code.

That leaves the backlog empty apart from the OTel entry, which is closed out as won't-fix above.

[Evangelink]

Update after two review rounds on #10384 - one backlog item was walked back:

• DotnetTestHttpClient new byte[1] -> won't fix. Hoisting it to an instance field was reverted. It saved one ~24-byte allocation per RPC on a path that already allocates a linked CTS, streams, ByteArrayContent and an HttpRequestMessage, and it coupled correctness to requests staying serialized by _requestLock forever. Not a good trade.
• SilenceDrivenHeartbeatRenderer.BuildSlowTestDescription -> done, with the builder created lazily so a healthy run that never surfaces a slow test still allocates nothing.
• AnsiTerminal.StopUpdate() -> done / unblocked, as described above.
• OpenTelemetryResultHandler.GetFullyQualifiedName() -> won't fix, as described above.

Net result: the two items with a real measurable win are fixed, the two negligible ones are closed out as won't-fix, and the backlog is empty.