The `ctest --test-load` option is implemented in `StartNextTests` by not
starting any tests when the load is too high and instead sleeping and
then returning. Prior to commit v3.11.0-rc1~117^2 (CTest: Re-implement
test process handling using libuv, 2017-12-10) our outer loop in
`RunTests` would immediately call `StartNextTests` again. However, now
the `uv_run` loop may simply terminate if there are no tests running
because no events are left pending.
Fix this by converting the sleep in `StartNextTests` into a libuv timer
that it starts instead. This avoids leaving `uv_run` with no pending
events. In the case that there are other running tests this also allows
CTest to detect when they finish even if it during the wait period where
we previously slept.
This regression was not caught by the test suite because it only
verified that we do not start new tests when the load was too high and
not that we proceed to start tests when the load drops. Revise the test
suite to cover both.
Fixes: #18338
Add documentation and tests for the existing
CTEST_CUSTOM_MAXIMUM_PASSED_TEST_OUTPUT_SIZE
CTEST_CUSTOM_MAXIMUM_FAILED_TEST_OUTPUT_SIZE
CTest variables.
Add variable CTEST_CHANGE_ID to configure the setting. This allows
CTest clients to give CDash information about what change is being
tested so that CDash can take actions to report the results (e.g. to a
pull request page).
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>
