From 0952338957fb1bca0751c59819bb51e8d356e8f4 Mon Sep 17 00:00:00 2001
From: Linwei Shang <linwei.shang@dfinity.org>
Date: Tue, 9 Jun 2026 15:15:26 -0400
Subject: [PATCH] ci: speed up Windows integration tests

The Windows test jobs spend ~10 min compiling in the "Run tests" step
while Ubuntu takes 1-2 min. The cache only stores third-party dependency
artifacts; workspace crates, the per-file integration test binaries, and
linking are recompiled every run, and that residual work is dominated by
slow MSVC linking + Defender file scanning on Windows.

Quick, CI-scoped wins (no structural change):

- CARGO_PROFILE_DEV_DEBUG=line-tables-only: drop full debuginfo so object
  files are smaller and link faster; keeps file:line in backtraces.
- Link windows-msvc with LLVM's lld-link (preinstalled on windows-2025)
  instead of link.exe. Scoped to this workflow, so the release/dist
  thin-LTO build keeps the default linker.
- Exclude the workspace and .cargo/.rustup from Windows Defender real-time
  scanning in both the unit-tests and test jobs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .github/workflows/test.yml | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index df40498c..aec1f747 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -13,6 +13,16 @@ env:
   CURL_HOME: .
   # Disable incremental compilation
   CARGO_INCREMENTAL: 0
+  # Reduce debug info in CI builds: smaller object files mean much faster
+  # linking (the dominant cost on Windows MSVC) and smaller caches.
+  # line-tables-only keeps file:line numbers in backtraces.
+  CARGO_PROFILE_DEV_DEBUG: line-tables-only
+  # Link with LLVM's lld-link instead of the slow MSVC link.exe. LLVM is
+  # preinstalled at C:\Program Files\LLVM on the windows-2025 image. This is
+  # only consumed when building the windows-msvc target, so it is a no-op on
+  # Linux/macOS, and being scoped to this workflow it does not affect the
+  # release/dist (thin-LTO) build, which keeps the default linker.
+  CARGO_TARGET_X86_64_PC_WINDOWS_MSVC_LINKER: "C:/Program Files/LLVM/bin/lld-link.exe"
   # These variables should be shared with WSL
   WSLENV: CARGO_INCREMENTAL:CURL_HOME/p:CARGO_NET_RETRY:GITHUB_ENV/p:GITHUB_OUTPUT/p
 
@@ -69,6 +79,17 @@ jobs:
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
+      # Defender real-time scanning of every object/rlib it writes slows
+      # file-heavy Rust builds and cache extraction considerably on Windows.
+      - name: Exclude build dirs from Windows Defender
+        if: ${{ contains(matrix.os, 'windows') }}
+        shell: pwsh
+        run: |
+          Add-MpPreference -ExclusionPath `
+            "$env:GITHUB_WORKSPACE", `
+            "$env:USERPROFILE\.cargo", `
+            "$env:USERPROFILE\.rustup" -ErrorAction SilentlyContinue
+
       - name: Setup image (Linux)
         if: ${{ contains(matrix.os, 'ubuntu') }}
         run: ./.github/scripts/provision-linux-build.sh
@@ -99,6 +120,17 @@ jobs:
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
+      # Defender real-time scanning of every object/rlib it writes slows
+      # file-heavy Rust builds and cache extraction considerably on Windows.
+      - name: Exclude build dirs from Windows Defender
+        if: ${{ contains(matrix.os, 'windows') }}
+        shell: pwsh
+        run: |
+          Add-MpPreference -ExclusionPath `
+            "$env:GITHUB_WORKSPACE", `
+            "$env:USERPROFILE\.cargo", `
+            "$env:USERPROFILE\.rustup" -ErrorAction SilentlyContinue
+
       - uses: actions-rust-lang/setup-rust-toolchain@150fca883cd4034361b621bd4e6a9d34e5143606 # v1.15.4
         with:
           cache-shared-key: ${{ runner.os }}-test