ctest: Optionally avoid starting tests that may exceed a given CPU load

Add a TestLoad setting to CTest that can be set via a new --test-load
command-line option, CTEST_TEST_LOAD variable, or TEST_LOAD option to
the ctest_test command.  Teach cmCTestMultiProcessHandler to measure
the CPU load and avoid starting tests that may take more than the
spare load currently available.  The expression

 <current_load> + <test_processors> <= <max-load>

must be true to start a new test.

Co-Author: Zack Galbreath <zack.galbreath@kitware.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/Tests/RunCMake/ctest_test/RunCMakeTest.cmake b/Tests/RunCMake/ctest_test/RunCMakeTest.cmake
index d906290..21d0447 100644
--- a/Tests/RunCMake/ctest_test/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ctest_test/RunCMakeTest.cmake
@@ -1,6 +1,8 @@
 include(RunCTest)
+set(RunCMake_TEST_TIMEOUT 60)
 
 set(CASE_CTEST_TEST_ARGS "")
+set(CASE_CTEST_TEST_LOAD "")
 
 function(run_ctest_test CASE_NAME)
   set(CASE_CTEST_TEST_ARGS "${ARGN}")
@@ -8,3 +10,42 @@ function(run_ctest_test CASE_NAME)
 endfunction()
 
 run_ctest_test(TestQuiet QUIET)
+
+# Tests for the 'Test Load' feature of ctest
+#
+# Spoof a load average value to make these tests more reliable.
+set(ENV{__CTEST_FAKE_LOAD_AVERAGE_FOR_TESTING} 5)
+
+# Verify that new tests are started when the load average falls below
+# our threshold.
+run_ctest_test(TestLoadPass TEST_LOAD 6)
+
+# Verify that new tests are not started when the load average exceeds
+# our threshold.
+run_ctest_test(TestLoadFail TEST_LOAD 2)
+
+# Verify that when an invalid "TEST_LOAD" value is given, a warning
+# message is displayed and the value is ignored.
+run_ctest_test(TestLoadInvalid TEST_LOAD "ERR1")
+
+# Verify that new tests are started when the load average falls below
+# our threshold.
+set(CASE_CTEST_TEST_LOAD 7)
+run_ctest_test(CTestTestLoadPass)
+
+# Verify that new tests are not started when the load average exceeds
+# our threshold.
+set(CASE_CTEST_TEST_LOAD 4)
+run_ctest_test(CTestTestLoadFail)
+
+# Verify that when an invalid "CTEST_TEST_LOAD" value is given,
+# a warning message is displayed and the value is ignored.
+set(CASE_CTEST_TEST_LOAD "ERR2")
+run_ctest_test(CTestTestLoadInvalid)
+
+# Verify that the "TEST_LOAD" value has higher precedence than
+# the "CTEST_TEST_LOAD" value
+set(CASE_CTEST_TEST_LOAD "ERR3")
+run_ctest_test(TestLoadOrder TEST_LOAD "ERR4")
+
+unset(ENV{__CTEST_FAKE_LOAD_AVERAGE_FOR_TESTING})