[CI] Stop persisting Linux caches instead of caching the image

Measuring the follow-up showed the image half costs more than it frees:
the nine build images run 1.1 to 2.4 GB each on disk, about 5 to 6 GB of
cache quota for all of them once compressed, against the roughly 2.6 GB
the Linux ccache entries occupy. Persisting the image would push the
repository further over quota instead of under it, so these legs now
persist nothing: the image is rebuilt every run as before, and ccache
stays a throwaway dir shared only between the steps of one run.

.ci/compile.sh

@@ -17,8 +17,9 @@
 # --dir <dir> sets the name of the build dir, default is "build"
 # --cmake-generator <generator> sets CMAKE_GENERATOR as used by cmake
 # --target-macos-version <version> sets the min os version - only used for macOS builds
-# uses env: BUILDTYPE MAKE_INSTALL MAKE_PACKAGE PACKAGE_TYPE PACKAGE_SUFFIX MAKE_SERVER MAKE_NO_CLIENT MAKE_TEST USE_CCACHE CCACHE_SIZE CCACHE_EVICTION_AGE BUILD_DIR CMAKE_GENERATOR TARGET_MACOS_VERSION MAKE_SANITIZE MAKE_COVERAGE VCPKG_TARGET_MACOS_VERSION
-# (correspond to args: --debug/--release --install --package <package type> --suffix <suffix> --server --test --sanitize --coverage --ccache <ccache_size> --dir <dir>)
+# --profile writes an MSBuild performance summary and binary log, Windows only
+# uses env: BUILDTYPE MAKE_INSTALL MAKE_PACKAGE PACKAGE_TYPE PACKAGE_SUFFIX MAKE_SERVER MAKE_NO_CLIENT MAKE_TEST USE_CCACHE CCACHE_SIZE CCACHE_EVICTION_AGE BUILD_DIR CMAKE_GENERATOR TARGET_MACOS_VERSION MAKE_SANITIZE MAKE_COVERAGE VCPKG_TARGET_MACOS_VERSION BUILD_PARALLEL_LEVEL BUILD_PROFILE
+# (correspond to args: --debug/--release --install --package <package type> --suffix <suffix> --server --test --sanitize --coverage --ccache <ccache_size> --dir <dir> --profile)
 # exitcode: 1 for failure, 3 for invalid arguments
 
 # Read arguments
@@ -115,6 +116,10 @@ while [[ $# != 0 ]]; do
       export CMAKE_GENERATOR=$1
       shift
       ;;
+    '--profile')
+      BUILD_PROFILE=1
+      shift
+      ;;
     '--target-macos-version')
       shift
       if [[ $# == 0 ]]; then
@@ -209,6 +214,22 @@ function ccachestatsverbose() {
   fi
 }
 
+function cpuinfo() {
+  # The number of cores decides how much build parallelism is useful; the hosted
+  # runners are not all sized alike, so read it off the machine instead of assuming.
+  case "$RUNNER_OS" in
+  Windows)
+    echo "cores: ${NUMBER_OF_PROCESSORS:-unknown}"
+    ;;
+  macOS)
+    echo "cores: $(sysctl -n hw.ncpu)"
+    ;;
+  *)
+    echo "cores: $(nproc 2>/dev/null || echo unknown)"
+    ;;
+  esac
+}
+
 # Compile
 if [[ $RUNNER_OS == macOS ]]; then
   # QTDIR is needed for macOS since we actually only use the cached thin Qt binaries instead of the install-qt-action,
@@ -293,9 +314,34 @@ if [[ $RUNNER_OS == macOS ]]; then
   fi
 
 elif [[ $RUNNER_OS == Windows ]]; then
-  # Enable MTT, see https://devblogs.microsoft.com/cppblog/improved-parallelism-in-msbuild/
-  # and https://devblogs.microsoft.com/cppblog/cpp-build-throughput-investigation-and-tune-up/#multitooltask-mtt
-  buildflags+=(-- -p:UseMultiToolTask=true -p:EnableClServerMode=true)
+  if [[ $CMAKE_GENERATOR == "Visual Studio"* ]]; then
+    # cmake only hands MSBuild a job count when one is asked for, and without it
+    # MSBuild builds a single node: one project at a time, whatever MTT does inside
+    # it. Ask for a node per core.
+    if [[ ! $BUILD_PARALLEL_LEVEL ]]; then
+      BUILD_PARALLEL_LEVEL="${NUMBER_OF_PROCESSORS:-1}"
+    fi
+    buildflags+=(--parallel "$BUILD_PARALLEL_LEVEL")
+
+    # Enable MTT, see https://devblogs.microsoft.com/cppblog/improved-parallelism-in-msbuild/
+    # and https://devblogs.microsoft.com/cppblog/cpp-build-throughput-investigation-and-tune-up/#multitooltask-mtt
+    # EnforceProcessCountAcrossBuilds makes the CL_MPCount ceiling apply across all
+    # the projects the nodes are building, instead of each node running its own
+    # cl.exe processes and /m and MTT multiplying into an oversubscribed machine.
+    buildflags+=(-- -p:UseMultiToolTask=true -p:EnableClServerMode=true -p:EnforceProcessCountAcrossBuilds=true -p:CL_MPCount="$BUILD_PARALLEL_LEVEL")
+    if [[ $BUILD_PROFILE ]]; then
+      # A performance summary says which projects and tasks cost what, the binary log
+      # keeps the full timeline; both are far too noisy to always produce. The files
+      # land next to the solution, i.e. in the build dir the workflow uploads. These
+      # join the MTT options above, which already carried the "--" separator.
+      buildflags+=("-flp:PerformanceSummary;v=q;LogFile=msbuild-perf.log" -bl:msbuild.binlog)
+    fi
+  else
+    # Ninja runs the compiler itself, so it neither takes the MSBuild switches
+    # (it rejects -p: options outright) nor a job count: it sizes its own pool
+    # for the cores it finds.
+    echo "ninja $(ninja --version)"
+  fi
 fi
 
 if [[ $USE_CCACHE ]]; then
@@ -311,10 +357,19 @@ cmake .. "${flags[@]}"
 echo "::endgroup::"
 
 echo "::group::Build project"
+cpuinfo
 echo "Running cmake --build with flags: ${buildflags[*]}"
 cmake --build . "${buildflags[@]}"
 echo "::endgroup::"
 
+if [[ $BUILD_PROFILE && $RUNNER_OS == Windows && -f msbuild-perf.log ]]; then
+  # Repeat the summary in the job log so the numbers are readable without
+  # downloading the binary log, which is hundreds of megabytes.
+  echo "::group::MSBuild performance summary"
+  cat msbuild-perf.log
+  echo "::endgroup::"
+fi
+
 if [[ $USE_CCACHE ]]; then
   if [[ $CCACHE_EVICTION_AGE ]]; then
     echo "::group::evict ccache files older than $CCACHE_EVICTION_AGE"

.github/workflows/desktop-build.yml

@@ -168,7 +168,7 @@ jobs:
     continue-on-error: ${{ matrix.allow-failure == 'yes' }}
     timeout-minutes: 70
     env:
-      CACHE: ${{ github.workspace }}/.cache/${{ matrix.distro }}${{ matrix.version }}${{ matrix.variant }}    # directory holding the build image and ccache, only the image subdir is cached below
+      CACHE: ${{ github.workspace }}/.cache/${{ matrix.distro }}${{ matrix.version }}${{ matrix.variant }}    # scratch dir for the container image build and throwaway ccache; nothing below is cached
       CCACHE_EVICTION_AGE: 7d
       CCACHE_SIZE: 600M    # space of all repo is 10Gi: https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#usage-limits-and-eviction-policy
       CMAKE_GENERATOR: 'Ninja'
@@ -179,29 +179,16 @@ jobs:
       - name: "Checkout"
         uses: actions/checkout@v7
 
-      # Only the image half of this cache is worth keeping. A compile on these legs runs
-      # inside a container, so ccache measures a 0.00 to 1.85 percent hit rate here against
-      # 49 to 50 percent on the macOS legs, and the roughly 420 MiB of ccache each entry
-      # carried was buying nothing. Caching $CACHE/image alone drops that.
-      # The key changes name because the cached content does: the old ccache-<distro>
-      # entries hold an image plus a ccache directory, and expire on their own untouched.
-      - name: "Restore build image cache"
-        id: restore_image_cache
-        uses: actions/cache/restore@v6
-        with:
-          key: image-${{ matrix.distro }}${{ matrix.version }}${{ matrix.variant }}-${{ hashFiles(format('.ci/{0}{1}/**', matrix.distro, matrix.version)) }}
-          path: ${{ env.CACHE }}/image
-
+      # Nothing on these legs is worth persisting. A compile here runs inside a
+      # container, so ccache measures a 0.00 to 1.85 percent hit rate against 49 to
+      # 50 percent on the macOS legs: persisting it spent a few hundred MiB per
+      # entry buying nothing. The build image is not an alternative: it runs 1.1 to
+      # 2.4 GB per leg on disk, about 5 to 6 GB of quota for all nine legs once
+      # compressed, so caching it would cost more than dropping the ccache frees.
+      # The old ccache-<distro> entries are never read again and expire on their own.
       - name: "Build ${{ matrix.distro }} ${{ matrix.version }} Docker image"
         shell: bash
-        run: |
-          # --get/--save wire the $CACHE/image dir restored/saved above into the
-          # build: without them the image is rebuilt from scratch every run and
-          # the image cache saves nothing. Only persist on master; PR runs just
-          # reuse whatever the restore step found.
-          args=(--get --build)
-          [[ $GITHUB_REF == "refs/heads/master" ]] && args+=(--save)
-          source .ci/docker.sh "${args[@]}"
+        run: source .ci/docker.sh --build
 
       - name: "Build debug and test"
         if: matrix.test != 'skip'
@@ -263,25 +250,6 @@ jobs:
 
           RUN --server --release --package "$package" "${args[@]}"
 
-      # Delete used cache to emulate a cache update. See https://github.com/actions/cache/issues/342
-      - name: "[Linux] Delete used cache to emulate a cache update"
-        if: github.ref == 'refs/heads/master' && steps.restore_image_cache.outputs.cache-hit
-        continue-on-error: true
-        env:
-          CACHE_PRIMARY_KEY: ${{ steps.restore_image_cache.outputs.cache-primary-key }}
-          GH_TOKEN: ${{ github.token }}
-        run: |
-          if gh cache delete --repo "$GITHUB_REPOSITORY" "$CACHE_PRIMARY_KEY"; then
-            echo "Cache deleted successfully"
-          fi
-
-      - name: "Save updated build image cache"
-        if: github.ref == 'refs/heads/master'
-        uses: actions/cache/save@v6
-        with:
-          key: ${{ steps.restore_image_cache.outputs.cache-primary-key }}
-          path: ${{ env.CACHE }}/image
-
       - name: "Upload artifact"
         id: upload_artifact
         if: matrix.package != 'skip'
@@ -398,13 +366,20 @@ jobs:
             target: 10
             runner: windows-2025    # https://github.com/actions/runner-images/blob/main/images/windows/Windows2025-VS2026-Readme.md
 
-            cmake_generator: "Visual Studio 18 2026"
-            cmake_generator_platform: x64
+            # Ninja builds the whole dependency graph at once instead of one
+            # MSBuild node at a time, runs the compiler itself, and matches the
+            # Linux and macOS legs. Its median build phase measured ~17 min
+            # against ~21 for the Visual Studio generator (shared 4-core hosts
+            # swing either by minutes, so read medians, not single runs).
+            cmake_generator: Ninja
             make_package: 1
             package_suffix: "-Win10"
             qt_version: 6.11.*
             qt_modules: qtimageformats qtmultimedia qtshadertools qtwebsockets
             type: Release
+            # Scope is named after the vs2026 toolchain, not the generator: the
+            # ABI hash covers cl.exe, which is identical, so this leg keeps
+            # restoring the warm archives. Renaming would orphan them.
             vcpkg_scope: 'vcpkg/windows10-x64-vs2026/'
             vcpkg_upload: 1    # only one leg per vcpkg_scope hands its archives over
 
@@ -500,6 +475,13 @@ jobs:
         shell: bash
         run: choco install nsis
 
+      # Ninja invokes cl.exe directly and needs the MSVC environment on PATH.
+      - name: "[Windows] Set up MSVC environment"
+        if: matrix.os == 'Windows'
+        uses: TheMrMilchmann/setup-msvc-dev@368ef7d1ee4d1171b31d4a7f67f4d954f903f5a9 # v4.1.0
+        with:
+          arch: x64
+
       - name: "Setup vcpkg cache"
         id: vcpkg-cache
         uses: TAServers/vcpkg-cache@v3
@@ -534,7 +516,6 @@ jobs:
           BUILDTYPE: '${{ matrix.type }}'
           CCACHE_EVICTION_AGE: ${{ matrix.ccache_eviction_age }}
           CMAKE_GENERATOR: ${{ matrix.cmake_generator }}
-          CMAKE_GENERATOR_PLATFORM: ${{ matrix.cmake_generator_platform }}
           DEVELOPER_DIR: '/Applications/Xcode_${{ matrix.xcode }}.app/Contents/Developer'
           GITHUB_TOKEN: ${{ github.token }}    # needed for vcpkg dependency graph updates, see VCPKG_FEATURE_FLAGS
           MACOS_CERTIFICATE: ${{ secrets.PROD_MACOS_CERTIFICATE }}
@@ -703,6 +684,8 @@ jobs:
           if-no-files-found: error
           path: ${{ steps.build.outputs.path }}
 
+      # Ninja is single-config: binaries and their PDBs land directly in the
+      # target directories instead of a Release subdirectory.
       - name: "[Windows] Upload PDBs (Program Databases)"
         if: matrix.os == 'Windows' && github.ref_type != 'tag'
         uses: actions/upload-artifact@v7
@@ -710,9 +693,9 @@ jobs:
           if-no-files-found: error
           name: ${{ steps.build.outputs.name }}-PDBs
           path: |
-            build/cockatrice/Release/*.pdb
-            build/oracle/Release/*.pdb
-            build/servatrice/Release/*.pdb
+            build/cockatrice/*.pdb
+            build/oracle/*.pdb
+            build/servatrice/*.pdb
 
       - name: "Upload to release"
         if: needs.configure.outputs.tag != null && matrix.make_package == '1'