Faster CI: Windows builds on D:, Defender and Spotlight off, parallel builds

.github/workflows/testpr.yaml

@@ -156,7 +156,7 @@ jobs:
       # while uploads go to a test channel, packages already there aren't built again
       ROBOSTACK_UPLOAD_CHANNEL: ${{ vars.ROBOSTACK_UPLOAD_CHANNEL }}
       # rattler-build writes to distros/<d>/work/output, or to CONDA_BLD_PATH (win-64)
-      CACHE_DIR: ${{ matrix.target.platform == 'win-64' && 'C:/bld/win-64' || format('distros/{0}/work/output/{1}', matrix.distro, matrix.target.platform) }}
+      CACHE_DIR: ${{ matrix.target.platform == 'win-64' && 'D:/bld/win-64' || format('distros/{0}/work/output/{1}', matrix.distro, matrix.target.platform) }}
     steps:
     - uses: actions/checkout@v6
       with:
@@ -167,6 +167,11 @@ jobs:
     # (e.g. vinca's), which breaks every later run restoring that cache
     - name: Disable git auto-maintenance
       run: git config --global maintenance.auto false && git config --global gc.auto 0 && git config --global core.longpaths true
+    # pixi's package cache on D:, with the builds' (see the Windows step below)
+    - name: "pixi's cache on D:"
+      if: runner.os == 'Windows'
+      shell: pwsh
+      run: '"PIXI_CACHE_DIR=D:\pixi-cache" | Out-File -FilePath $env:GITHUB_ENV -Append'
     - uses: prefix-dev/setup-pixi@v0.11.0
       with:
         locked: true  # the lock file must match pixi.toml
@@ -177,12 +182,25 @@ jobs:
       if: runner.os == 'Windows'
       shell: pwsh
       run: |
-        "CONDA_BLD_PATH=C:\bld\" | Out-File -FilePath $env:GITHUB_ENV -Append
-        New-Item -ItemType Directory -Force -Path C:\bld | Out-Null
+        # Defender's real-time scan slows down installing and deleting the environments'
+        # files several times over; the runner is thrown away after the job
+        Set-MpPreference -DisableRealtimeMonitoring $true
+        # the builds, rattler's package cache (on the same drive, for hardlinks) and the
+        # temporary files on D:, about three times as fast as C: on GitHub's runners
+        "CONDA_BLD_PATH=D:\bld\", "RATTLER_CACHE_DIR=D:\rattler", "TMP=D:\tmp", "TEMP=D:\tmp" |
+          Out-File -FilePath $env:GITHUB_ENV -Append
+        New-Item -ItemType Directory -Force -Path D:\bld, D:\rattler, D:\tmp | Out-Null
+        Get-PSDrive C, D | Format-Table Name, @{n="free GB"; e={[math]::Round($_.Free / 1GB)}}
         New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem" -Name "LongPathsEnabled" -Value 1 -PropertyType DWORD -Force
         Remove-Item -Recurse -Force C:\Strawberry -ErrorAction SilentlyContinue
         Remove-Item -Recurse -Force "C:\Program Files (x86)\Windows Kits\10\Include\10.0.17763.0" -ErrorAction SilentlyContinue
 
+    # Spotlight indexes every file the environments and builds write, using up to a
+    # core or two of the runner's three or four; the runner is thrown away after the job
+    - name: Turn off Spotlight
+      if: runner.os == 'macOS'
+      run: sudo mdutil -a -i off || true
+
     - name: Clean up PATH
       if: runner.os == 'Windows'
       uses: egor-tensin/cleanup-path@v5
@@ -242,6 +260,9 @@ jobs:
         extra=()
         # shorter work dirs for MAX_PATH on Windows
         [ "$PLATFORM" == "win-64" ] && extra+=(--no-build-id)
+        # independent recipes side by side, with a shared jobserver keeping them at the
+        # runner's cores in total; Windows has no jobserver, and was no faster with two
+        [ "$PLATFORM" != "win-64" ] && extra+=(--parallel-builds "3:$(getconf _NPROCESSORS_ONLN)")
         pixi run rs "$DISTRO" build --target-platform "$PLATFORM" "${extra[@]}" 2>&1 | tee rattler-build.log
         status=${PIPESTATUS[0]}
         echo "exit-code=${status}" >> "$GITHUB_OUTPUT"

.scripts/build_unix.sh

@@ -24,16 +24,19 @@ export "CONDA_BLD_PATH=$HOME/conda-bld/"
 
 if [[ "$target" == *"osx"* ]]; then
     echo "osx"
+    # Spotlight indexes every file the environments and builds write, using up to a
+    # core or two of the runner's three or four; the runner is thrown away after the job
+    sudo mdutil -a -i off || true
     export PATH=$(echo $PATH | tr ":" "\n" | grep -v 'homebrew' | xargs | tr ' ' ':')
 fi
 
+# All of the job's recipes in one build-ci run (tools/robostack.py), which builds
+# independent ones in parallel and adds the variant config and the distro's channels.
+recipe_args=()
 for recipe in ${CURRENT_RECIPES[@]}; do
-	# build-ci (tools/robostack.py) adds the variant config and the distro's channels.
-	pixi run -v rs "${ROBOSTACK_DISTRO}" build-ci \
-		--recipe ${FEEDSTOCK_ROOT}/recipes/${recipe} \
-		--output-dir $CONDA_BLD_PATH
-
+	recipe_args+=(--recipe "${FEEDSTOCK_ROOT}/recipes/${recipe}")
 done
+pixi run -v rs "${ROBOSTACK_DISTRO}" build-ci "${recipe_args[@]}" --output-dir $CONDA_BLD_PATH
 
 # Check if it build something, this is a hotfix for the skips inside additional_recipes
 shopt -s nullglob

.scripts/build_win.bat

@@ -1,7 +1,19 @@
 
 setlocal EnableExtensions EnableDelayedExpansion
 
-set CONDA_BLD_PATH=C:\bld
+:: Defender's real-time scan slows down installing and deleting the environments'
+:: files several times over; the runner is thrown away after the job
+powershell -NoProfile -Command "Set-MpPreference -DisableRealtimeMonitoring $true"
+
+:: The builds, rattler's package cache (on the same drive, for hardlinks) and the
+:: temporary files on D:, about three times as fast as C: on GitHub's runners
+set CONDA_BLD_PATH=D:\bld
+set VINCA_CUSTOM_CMAKE_BUILD_DIR=D:\x\
+set RATTLER_CACHE_DIR=D:\rattler
+set TMP=D:\tmp
+set TEMP=D:\tmp
+mkdir D:\tmp
+powershell -NoProfile -Command "Get-PSDrive C, D | Format-Table Name, @{n='free GB'; e={[math]::Round($_.Free / 1GB)}}"
 echo "PATH is %PATH%"
 
 rmdir /Q/S C:\Strawberry\
@@ -18,16 +30,12 @@ reg add HKLM\SYSTEM\CurrentControlSet\Control\FileSystem /v LongPathsEnabled /t
 :: ... and in git, for sources that vendor packages clone during the build
 git config --global core.longpaths true
 
-for %%X in (%CURRENT_RECIPES%) do (
-    echo "BUILDING RECIPE %%X"
-    cd %FEEDSTOCK_ROOT%\recipes\%%X\
-    rem build-ci (tools/robostack.py) adds the variant config and the distro's channels.
-    pixi run -v rs %ROBOSTACK_DISTRO% build-ci --recipe %FEEDSTOCK_ROOT%\recipes\%%X\ ^
-        --output-dir %CONDA_BLD_PATH%
-
-    if errorlevel 1 exit 1
-    rem -m %FEEDSTOCK_ROOT%\.ci_support\conda_forge_pinnings.yaml
-)
+:: All of the job's recipes in one build-ci run (tools/robostack.py), which builds
+:: independent ones in parallel and adds the variant config and the distro's channels.
+set RECIPE_ARGS=
+for %%X in (%CURRENT_RECIPES%) do set "RECIPE_ARGS=!RECIPE_ARGS! --recipe %FEEDSTOCK_ROOT%\recipes\%%X\"
+pixi run -v rs %ROBOSTACK_DISTRO% build-ci !RECIPE_ARGS! --output-dir %CONDA_BLD_PATH%
+if errorlevel 1 exit 1
 
 :: Check if .conda files exist in the win-64 directory
 if exist "%CONDA_BLD_PATH%\win-64\*.conda" (

pixi.toml

@@ -17,7 +17,7 @@ PYTHONIOENCODING = "utf-8"
 
 [dependencies]
 python = ">=3.14.0,<3.15"
-rattler-build = ">=0.76.1,<0.77"
+rattler-build = ">=0.77.0,<0.78"
 cmake = "<4.0"
 setuptools = "<82.0"
 rattler-index = ">=0.27.16"

tools/build_timings.py

@@ -87,18 +87,26 @@ def dumps(recipes: dict) -> str:
     return "{\n" + ",\n".join(lines) + "\n}\n"
 
 
-def vinca_timings(distro: str, platform: str, path: Path) -> bool:
-    """Write vinca-gha's --timings file for the platform: each recipe's average over the
-    distributions, and ALIAS_SECONDS for the distribution's compatibility recipes
-    (ros-<distro>-<name>, built right after ros2-<name>). False when there are no times yet."""
+def timings(distro: str, platform: str) -> dict | None:
+    """{"recipes": {recipe: seconds}, "default": seconds} for the platform: each recipe's
+    average over the distributions, and ALIAS_SECONDS for the distribution's compatibility
+    recipes (ros-<distro>-<name>, built right after ros2-<name>). None without times yet."""
     source = TIMINGS / f"{platform}.json"
     if not source.is_file():
-        return False
+        return None
     recipes = {r: round(statistics.fmean(by.values()), 1) for r, by in json.loads(source.read_text()).items()}
     # unmeasured recipes: the median of the packages (ros2-*)
     default = statistics.median([s for r, s in recipes.items() if r.startswith("ros2-")] or list(recipes.values()))
     recipes.update({f"ros-{distro}-{r[len('ros2-'):]}": ALIAS_SECONDS for r in list(recipes) if r.startswith("ros2-")})
-    path.write_text(json.dumps({"recipes": recipes, "default": default}) + "\n")
+    return {"recipes": recipes, "default": default}
+
+
+def vinca_timings(distro: str, platform: str, path: Path) -> bool:
+    """Write vinca-gha's --timings file for the platform (timings()); False when there are
+    no times yet."""
+    if (data := timings(distro, platform)) is None:
+        return False
+    path.write_text(json.dumps(data) + "\n")
     return True
 
 

tools/ci_estimate.py

@@ -3,9 +3,10 @@
     python tools/ci_estimate.py --recipes distros/<d>/work/recipes --cache-dir <dir> --platform <p>
 
 Recipes whose package is in the restored cache are skipped by rattler-build; the rest
-are built. The seconds per package below are rough averages from the jazzy full
-rebuild in October 2026 (wall clock of the build step, including environment setup):
-building one package, and skipping one that is already in the cache.
+are built, each taking its measured time (shared/build_timings, see build_timings.py).
+The seconds per package below are rough averages from the jazzy full rebuild in October
+2026 (wall clock of the build step, including environment setup): building one package,
+for platforms without measured times, and skipping one that is already in the cache.
 """
 
 import argparse
@@ -14,6 +15,8 @@
 import sys
 from pathlib import Path
 
+import build_timings
+
 SECONDS = {  # platform: (per built package, per skipped package)
     "linux-64": (19, 2),
     "linux-aarch64": (21, 3),
@@ -45,7 +48,12 @@ def main() -> int:
     to_build = sorted(recipes - cached)
     skipped = len(recipes & cached)
     build, skip = SECONDS.get(args.platform, max(SECONDS.values()))
-    seconds = len(to_build) * build + skipped * skip
+    distro = args.recipes.resolve().parent.parent.name  # distros/<distro>/work/recipes
+    measured = build_timings.timings(distro, args.platform)
+    if measured:
+        seconds = sum(measured["recipes"].get(r, measured["default"]) for r in to_build) + skipped * skip
+    else:
+        seconds = len(to_build) * build + skipped * skip
     hours = seconds / 3600
     rounds = int(hours // JOB_LIMIT_HOURS) + 1
     done = datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(seconds=seconds)