CTest: Add options to control test process affinity to CPUs

In commit v2.8.0~170 (ENH: Added ctest test options PROCESSORS and
RUN_SERIAL, 2009-09-07) CTest learned to track the number of processors
allocated to running tests in order to balance it against the desired
level of parallelism.  Extend this idea by introducing a new
`PROCESSOR_AFFINITY` test property to ask that CTest run a test
with the CPU affinity mask set.  This will allow a set of tests
that are running concurrently to use disjoint CPU resources.

5 files changed, 45 insertions, 0 deletions

diff --git a/Tests/CMakeLib/CMakeLists.txt b/Tests/CMakeLib/CMakeLists.txt
index 06df53f..126076d 100644
--- a/Tests/CMakeLib/CMakeLists.txt
+++ b/Tests/CMakeLib/CMakeLists.txt
@@ -49,3 +49,6 @@ if(TEST_CompileCommandOutput)
 endif()
 
 add_subdirectory(PseudoMemcheck)
+
+add_executable(testAffinity testAffinity.cxx)
+target_link_libraries(testAffinity CMakeLib)
diff --git a/Tests/CMakeLib/testAffinity.cxx b/Tests/CMakeLib/testAffinity.cxx
new file mode 100644
index 0000000..4b82280
--- /dev/null
+++ b/Tests/CMakeLib/testAffinity.cxx
@@ -0,0 +1,18 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#include "cmAffinity.h"
+
+#include <cstddef>
+#include <iostream>
+#include <set>
+
+int main()
+{
+  std::set<size_t> cpus = cmAffinity::GetProcessorsAvailable();
+  if (!cpus.empty()) {
+    std::cout << "CPU affinity mask count is '" << cpus.size() << "'.\n";
+  } else {
+    std::cout << "CPU affinity not supported on this platform.\n";
+  }
+  return 0;
+}
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index 31069fa..beadb1d 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -339,6 +339,9 @@ add_RunCMake_test(CPackConfig)
 add_RunCMake_test(CPackInstallProperties)
 add_RunCMake_test(ExternalProject)
 add_RunCMake_test(FetchContent)
+if(NOT CMake_TEST_EXTERNAL_CMAKE)
+  set(CTestCommandLine_ARGS -DTEST_AFFINITY=$<TARGET_FILE:testAffinity>)
+endif()
 add_RunCMake_test(CTestCommandLine)
 add_RunCMake_test(CacheNewline)
 # Only run this test on unix platforms that support
diff --git a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
index 0fafea5..3033c9c 100644
--- a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
@@ -141,3 +141,23 @@ function(run_TestOutputSize)
     )
 endfunction()
 run_TestOutputSize()
+
+function(run_TestAffinity)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/TestAffinity)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
+  file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
+  # Create a test with affinity enabled.  The default PROCESSORS
+  # value is 1, so our expected output checks that this is the
+  # number of processors in the mask.
+  file(WRITE "${RunCMake_TEST_BINARY_DIR}/CTestTestfile.cmake" "
+  add_test(Affinity \"${TEST_AFFINITY}\")
+  set_tests_properties(Affinity PROPERTIES PROCESSOR_AFFINITY ON)
+")
+  # Run ctest with a large parallel level so that the value is
+  # not responsible for capping the number of processors available.
+  run_cmake_command(TestAffinity ${CMAKE_CTEST_COMMAND} -V -j 64)
+endfunction()
+if(TEST_AFFINITY)
+  run_TestAffinity()
+endif()
diff --git a/Tests/RunCMake/CTestCommandLine/TestAffinity-stdout.txt b/Tests/RunCMake/CTestCommandLine/TestAffinity-stdout.txt
new file mode 100644
index 0000000..e23d30b
--- /dev/null
+++ b/Tests/RunCMake/CTestCommandLine/TestAffinity-stdout.txt
@@ -0,0 +1 @@
+1: CPU affinity (mask count is '1'|not supported on this platform)\.