[perf-improver] Monthly Activity 2026-06

[Evangelink]

Activity for June 2026

Suggested Actions for Maintainer

• Review PR (perf-assist/defer-class-cleanup-context-alloc): perf: defer class-cleanup TestContextImplementation allocation to only the last test in each class — check recent PRs

Performance Opportunities Backlog

1. [Done ✅ PR [perf-improver] perf: single-pass PropertyBag walk in TerminalOutputDevice and SimplifiedConsoleOutputDeviceBase #9159 merged] Single-pass PropertyBag walk in TerminalOutputDevice / SimplifiedConsoleOutputDeviceBase
2. [Done ✅ PR [perf-improver] perf: replace per-test Queue/Stack copies with List-based index iteration in TestMethodInfo lifecycle #9257 merged] Eliminate per-test Queue / Stack allocation in MSTest adapter lifecycle
3. [Done ✅ PR [perf-improver] Replace Array.IndexOf(GetType()) with 'is' pattern matching in hot paths #9299 merged] Replace Array.IndexOf(GetType()) with is pattern matching in TestApplicationResult, AbortForMaxFailedTestsExtension, RetryDataConsumer
4. [Done ✅ PR [perf-improver] Extend performance runner timing scenarios to Linux/macOS and add ClassLevel variant #9311 merged] Extend performance runner timing scenarios to Linux/macOS; add ClassLevel variant
5. [Done ✅ PR [perf-improver] perf: avoid redundant TestNodeUid allocation in PopulateTestNodeStatistics #9348 merged] Avoid redundant TestNodeUid allocation in PerRequestServerDataConsumer.PopulateTestNodeStatistics (server mode, 2×N per test run)
6. [Done ✅ PR [perf-improver] perf: skip unused TestContextImplementation allocations for repeat assembly/class init #9433 merged] Skip unused TestContextImplementation allocations in UnitTestRunner.RunSingleTestAsync: for tests 2+ in an assembly/class, ~2 dictionary copies + 2 CancellationTokenRegistration allocs skipped per test
7. [Done ✅ PR [perf-improver] perf: add Linux job to nightly perf-timing workflow #9450 merged] Add Linux job to nightly perf-timing workflow
8. [PR submitted this run] Defer class-cleanup TestContextImplementation allocation to last test only in RunSingleTestAsync — same pattern as [perf-improver] perf: skip unused TestContextImplementation allocations for repeat assembly/class init #9433, saves C×(K−1) allocations for C classes averaging K tests each (branch perf-assist/defer-class-cleanup-context-alloc)
9. AntiTerminal.StopUpdate() — _stringBuilder.ToString() allocates on every terminal-output flush; blocked on IConsole interface limitation (netstandard2.0 target). Low priority.
10. SilenceDrivenHeartbeatRenderer — allocations only on rare heartbeat/slow-test paths; not a hot path. Low priority.
11. ClassifyOutcome in TestResultCaptureHelper.cs — add explicit CancelledTestNodeStateProperty arm to avoid Array.IndexOf fallback for obsolete type. Very low priority.

Discovered Commands

# Build all projects (Debug)
./build.sh

# Build + run unit tests
./build.sh -test

# Pack NuGet packages (required before acceptance tests and performance runner)
./build.sh -pack

# Run acceptance integration tests (requires -pack first)
./build.sh -pack -test -integrationTest

# Run performance timing scenarios (requires -pack first)
.dotnet/dotnet run --project test/Performance/MSTest.Performance.Runner \
  -- execute --pipelineNameFilter "*PlainProcess*"

# Run a single test project (using installed SDK in .dotnet/)
.dotnet/dotnet run --project <project-path> -f net9.0 --no-build -- --treenode-filter "*/*/MyTestClass/*"

Run History

2026-06-26 15:00 UTC - Run

• 📋 Task 4: Confirmed PR [perf-improver] perf: skip unused TestContextImplementation allocations for repeat assembly/class init #9433 (skip-unused-init-contexts) and PR [perf-improver] perf: add Linux job to nightly perf-timing workflow #9450 (Linux perf-timing job) both merged 2026-06-26 — no open perf-improver PRs remaining
• 🔍 Task 2/3: Scanned UnitTestRunner.cs hot paths — found testContextForClassCleanup allocated unconditionally for every test even when isLastTestInClass is false and context is never used
• 🔧 Task 3: Submitted PR on branch perf-assist/defer-class-cleanup-context-alloc — defer class-cleanup TestContextImplementation to last test only; saves C×(K−1) allocations per run (same pattern as [perf-improver] perf: skip unused TestContextImplementation allocations for repeat assembly/class init #9433)

2026-06-25 14:30 UTC - Run

• 🔧 Task 3: Submitted draft PR on branch perf-assist/skip-unused-init-contexts — skip unused TestContextImplementation allocations in RunSingleTestAsync: for tests 2+ in an assembly/class, avoids ~2 dictionary copies + 2 CancellationTokenRegistration register/dispose pairs per test — MERGED as PR [perf-improver] perf: skip unused TestContextImplementation allocations for repeat assembly/class init #9433 on 2026-06-26
• 🔍 Task 2: Confirmed no new high-value targets beyond the submitted PR
• 🧹 Task 7: Cleaned up broken #aw_linux_perf placeholder (Linux perf-timing PR was never created in run 28105007003)

2026-06-24 14:17 UTC - Run

• 🔍 Task 2: Surveyed hot paths — no new high-value code targets found; efficiency-improver covered DotnetTestDataConsumer ([efficiency-improver] perf: single-pass PropertyBag collection in DotnetTestDataConsumer #9380) merged same day
• 🔧 Task 6: Attempted to create PR to add parallel ubuntu-latest job to perf-timing-nightly.yml — PR not created this run; created as PR [perf-improver] perf: add Linux job to nightly perf-timing workflow #9450 on 2026-06-26 and MERGED same day

2026-06-23 UTC - Run

• 🔍 Tasks 2/3: Scanned MTP and MSTest adapter hot paths — all previously identified opportunities now merged; no new high-value targets found this run
• 📝 Confirmed PR [perf-improver] perf: avoid redundant TestNodeUid allocation in PopulateTestNodeStatistics #9348 (avoid redundant TestNodeUid allocation) merged by Evangelink on 2026-06-23

2026-06-19 UTC - Run

• 🔍 Task 4: Verified all previous PRs ([perf-improver] Replace Array.IndexOf(GetType()) with 'is' pattern matching in hot paths #9299, [perf-improver] Extend performance runner timing scenarios to Linux/macOS and add ClassLevel variant #9311) merged and issue [perf-improver] Track performance regressions in CI: integrate MSTest.Performance.Runner timing output #9312 closed — no maintenance needed
• 🔍 Task 2/3: Scanned server-mode execution path; found unnecessary new TestNodeUid(message.TestNode.Uid.Value) allocation in PopulateTestNodeStatistics
• 🔧 Created PR [perf-improver] perf: avoid redundant TestNodeUid allocation in PopulateTestNodeStatistics #9348: Avoid redundant TestNodeUid allocation (server mode, saves ~2×N short-lived allocations per test run) — MERGED by Evangelink on 2026-06-23

2026-06-21 14:14 UTC - Run

• 🔍 Task 6: Audited MSTest.Performance.Runner — found cross-platform timing gap (PlainProcess/DotnetTrace registered Windows-only despite using cross-platform APIs)
• 🔧 Created PR [perf-improver] Extend performance runner timing scenarios to Linux/macOS and add ClassLevel variant #9311: Extend performance runner timing scenarios to Linux/macOS; add ClassLevel parallelism variant — MERGED by Evangelink on 2026-06-22
• 📋 Created issue [perf-improver] Track performance regressions in CI: integrate MSTest.Performance.Runner timing output #9312: Proposal to integrate MSTest.Performance.Runner timing into CI for regression detection — CLOSED (implemented by Evangelink in PR Add Phase 1 nightly perf-timing CI workflow (#9312) #9325)
• 🔍 Task 4: PR [perf-improver] Replace Array.IndexOf(GetType()) with 'is' pattern matching in hot paths #9299 CI checks all green

2026-06-20 14:30 UTC - Run

• 🔍 Scanned TrxReport, HtmlReport, Retry, TestContext — confirmed well-optimized; identified Array.IndexOf(GetType()) redundancy in per-test hot paths
• 🔧 Created PR [perf-improver] Replace Array.IndexOf(GetType()) with 'is' pattern matching in hot paths #9299: Replace Array.IndexOf(GetType()) with is pattern matching — MERGED by Evangelink on 2026-06-22
• 📊 Build: ✅ 0 errors/warnings; MTP unit tests: ✅ 1220 passed; Extensions unit tests: ✅ 539 passed

2026-06-17 - Run

• 🔧 Created PR [perf-improver] perf: replace per-test Queue/Stack copies with List-based index iteration in TestMethodInfo lifecycle #9257: perf: replace per-test Queue/Stack copies with List-based index iteration in TestMethodInfo lifecycle — MERGED by Evangelink on 2026-06-19
• 🔍 Confirmed PropertyBag SingleOrDefault() is already O(1) via _testNodeStateProperty fast-path
• 📊 Verified: 89/89 TestMethodInfoTests pass, 50/50 TypeCacheTests pass, full build succeeds 0 warnings

2026-06-15 - Run

• 🔧 Created PR [perf-improver] perf: single-pass PropertyBag walk in TerminalOutputDevice and SimplifiedConsoleOutputDeviceBase #9159: perf: single-pass PropertyBag walk in TerminalOutputDevice — MERGED by Evangelink on 2026-06-16
• 🔍 Identified per-test Queue/Stack allocation in TestMethodInfo.Lifecycle.cs as next optimization target

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