[perf-improver] perf: pass cached ParameterTypes to GetInvokeResultAsync to avoid per-invocation GetParameters() allocation

[github-actions]

Goal

Eliminate one (or two for generic methods) ParameterInfo[] heap allocations per test invocation in the MSTest execution hot path.

Background

MethodInfo.GetParameters() is a CLR-mandated copy-on-every-call API: the runtime keeps an internal ParameterInfo[] but returns a fresh copy to each caller to prevent external mutation of internal state. This means every call allocates a new array on the heap, even when the method signature hasn't changed between invocations.

TestMethodInfo.ParameterTypes already caches this result via field ??= MethodInfo.GetParameters() (introduced in #9514). However, the two GetInvokeResultAsync call sites in TestMethodInfo.Execution.cs passed only the raw MethodInfo:

// Both call sites, called once per test execution:
Task? invokeResult = MethodInfo.GetInvokeResultAsync(_classInstance, arguments);

Inside GetInvokeResultAsync, line 121 then called:

ParameterInfo[]? methodParameters = methodInfo.GetParameters(); // fresh alloc every call

For generic test methods, ConstructGenericMethod (called from the same method) called GetParameters() again — a second allocation for the same data.

Approach

1. Add a GetInvokeResultAsync overload that accepts a pre-cached ParameterInfo[] parameter.
2. Keep the existing params overload as a thin wrapper that calls GetParameters() once and delegates — all non-hot-path callers (assembly init/cleanup, class init/cleanup, TestInitialize/TestCleanup) are unchanged.
3. Update ConstructGenericMethod's signature to accept the ParameterInfo[] instead of calling GetParameters() internally.
4. Update the two hot-path call sites in TestMethodInfo.Execution.cs to pass the cached ParameterTypes property.

Performance Evidence

Scenario	Before	After
Standard test (non-generic)	1 ParameterInfo[] alloc per invocation	0 (uses cached ParameterTypes)
Generic test method	2 ParameterInfo[] allocs per invocation	0 (both sites use cached value)

For a suite with N tests, this eliminates N–2N short-lived heap allocations. Fewer short-lived objects → reduced GC pressure → lower pause frequency.

The ParameterTypes cache is valid for the lifetime of the TestMethodInfo instance: MethodInfo is get-only and set once in the constructor.

Trade-offs

Minimal. The additional overload is a 1-line delegation. All callers not on the hot path continue to use the original params overload unchanged. The correctness argument is straightforward: TestMethodInfo.ParameterTypes caches this.MethodInfo.GetParameters() and GetInvokeResultAsync is called with this.MethodInfo, so the cached value is identical to what GetParameters() would return inside the method.

Reproducibility

Any test suite exercises both paths. For direct allocation measurement, run BenchmarkDotNet on a parameterised test method:

./build.sh -pack
# Then run the performance runner:
.dotnet/dotnet run --project test/Performance/MSTest.Performance.Runner -- execute --pipelineNameFilter "*PlainProcess*"

Test Status

./build.sh -test — all unit tests pass (net8.0 + net9.0).

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Show patch preview (102 of 102 lines)

From 3c9ccc0f85548d0ed38022f63f30a276e67627da Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Mon, 6 Jul 2026 14:58:05 +0000
Subject: [PATCH] perf: pass cached ParameterTypes to GetInvokeResultAsync to
 avoid per-invocation GetParameters() allocation

MethodInfo.GetParameters() always returns a fresh ParameterInfo[] copy on
every call. TestMethodInfo.ParameterTypes already caches this via 'field ??='
lazy initialisation (added in #9514).

However, the two GetInvokeResultAsync call sites in TestMethodInfo.Execution.cs
passed only the raw MethodInfo, causing GetInvokeResultAsync to call
GetParameters() internally on every single test invocation.

For a suite with N tests this eliminates N ParameterInfo[] allocations. For
generic test methods the saving doubles: ConstructGenericMethod previously
called GetParameters() again on the same MethodInfo.

Changes:
- Add GetInvokeResultAsync overload that accepts a ParameterInfo[] directly.
- Keep the params overload as a thin wrapper (calls GetParameters() once,
 delegates to the new overload); all non-hot-path callers are unchanged.
- Update ConstructGenericMethod signature to accept ParameterInfo[] instead
 of calling GetParameters() internally.
- Update the two hot-path call sites in TestMethodInfo.Execution.cs to pass
 the already-cached ParameterTypes property.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../Execution/TestMethodInfo.Execution.cs | 4 ++--
 .../Extensions/MethodInfoExtensions.cs | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.Execution.cs b/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.Execution.cs
index 6515ea5..1d3f7d5 100644
--- a/src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodInfo.Execution.cs
+++ b/src/Adapter/MSTestAdapter.PlatformServices/Execu
... (truncated)