Compare to Dev Drive:

.github/workflows/ci.yml

@@ -250,6 +250,40 @@ jobs:
         env:
           TEMP: "C:\\Temp"
 
+      - run: rm .nox -r
+
+      - name: Create a Dev Drive
+        run: |
+          ./tools/ci/devdrive.ps1 -Drive R -Size 4GB
+          mkdir R:/Temp
+          echo "TEMP=R:\\Temp" >> $env:GITHUB_ENV
+          Copy-Item -Path ${{ github.workspace }} -Destination "R:/pip" -Recurse
+
+      # Main check
+      - name: Run unit tests
+        if: matrix.group == 1
+        working-directory: R:/pip
+        run: >-
+          nox -s test-${{ matrix.python }} --
+          -m unit
+          --verbose --numprocesses auto --showlocals
+
+      - name: Run integration tests (group 1)
+        if: matrix.group == 1
+        working-directory: R:/pip
+        run: >-
+          nox -s test-${{ matrix.python }} --
+          -m integration -k "not test_install"
+          --verbose --numprocesses auto --showlocals
+
+      - name: Run integration tests (group 2)
+        if: matrix.group == 2
+        working-directory: R:/pip
+        run: >-
+          nox -s test-${{ matrix.python }} --
+          -m integration -k "test_install"
+          --verbose --numprocesses auto --showlocals
+
   tests-zipapp:
     name: tests / zipapp
     runs-on: ubuntu-latest

tools/ci/devdrive.ps1

@@ -0,0 +1,39 @@
+# A Powershell script to create a Dev Drive which tends to have significantly better
+# performance in developer workloads. The goal is improve pip's Windows CI times.
+#
+# The implementation was borrowed from the uv project which also use a Dev Drive for
+# better CI performance: https://github.com/astral-sh/uv/pull/3522
+#
+# Windows docs:
+#   https://learn.microsoft.com/en-us/windows/dev-drive/
+# Related GHA reports:
+#   https://github.com/actions/runner-images/issues/7320 (Windows slowness report)
+#   https://github.com/actions/runner-images/issues/8698 (feature request for
+#     preprovisioned Dev Drives)
+
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory=$true,
+    HelpMessage="Drive letter to use for the Dev Drive")]
+    [String]$drive,
+    [Parameter(Mandatory=$true,
+    HelpMessage="Size to allocate to the Dev Drive")]
+    [UInt64]$size
+)
+$ErrorActionPreference = "Stop"
+
+$OSVersion = [Environment]::OSVersion.Version
+$Partition = New-VHD -Path D:/pip_dev_drive.vhdx -SizeBytes $size |
+          Mount-VHD -Passthru |
+          Initialize-Disk -Passthru |
+          New-Partition -DriveLetter $drive -UseMaximumSize
+# Dev Drives aren't supported on all GHA Windows runners, in which case fallback to
+# a ReFS disk which still offer performance gains.
+if ($OSVersion -ge (New-Object 'Version' 10.0.22621)) {
+    Write-Output "Dev Drives are supported, one will be created at ${drive}:"
+    $Volume = ($Partition | Format-Volume -DevDrive -Confirm:$false -Force)
+} else {
+    Write-Output "Dev Drives are unsupported, only creating a ReFS disk at ${drive}:"
+    $Volume = ($Partition | Format-Volume -FileSystem ReFS -Confirm:$false -Force)
+}
+Write-Output $Volume