[Darwin] Limit parallelism for sanitizer tests that use shadow memory on AS

[yln]

Summary

On Darwin, we want to limit the parallelism during test execution for
sanitizer tests that use shadow memory. The reason is explained by this
existing comment:

Only run up to 3 processes that require shadow memory simultaneously
on 64-bit Darwin. Using more scales badly and hogs the system due to
inefficient handling of large mmap'd regions (terabytes) by the
kernel.

Previously we detected 3 cases:

• on-device: limit to 1 process
• 64-bit: macOS & simulators, limit to 3 processes
• others (32-bit): no limitation

We checked for the 64-bit case like this: `if arch in ['x86_64',
'x86_64h']` which misses macOS running on AS. Additionally, we don't
care about 32-bit anymore, so I've simplified this to 2 cases: on-device
and everything else.

[delcypher]

Changes seems good. I certainly like that we've simplified things. If we can resolve the question I asked then I think this will be good to go.

compiler-rt/test/asan/Unit/lit.site.cfg.py.in

65

How do we ensure this change doesn't effect non-Darwin hosts?

Previously we would only assign a parallelism group on Darwin hosts, now we don't have that check anymore.

Is it okay to do this because assigning a parallelism group on its own won't change anything. Presumably it also requires the lit_config.parallelism_groups['shadow-memory'] = 3 setting which is guarded by platform.system() == 'Darwin'?

[yln]

compiler-rt/test/asan/Unit/lit.site.cfg.py.in

65

Yes, that's right. There is two steps:

• Assigning a parallelism group to test configs, that is, declare that "tests for this tool setup shadow memory".
• Per platform configuration of the constraints:

# No throttling on non-Darwin platforms.
lit_config.parallelism_groups['shadow-memory'] = None

if platform.system() == 'Darwin':
  ios_device = config.apple_platform != 'osx' and not config.apple_platform.endswith('sim')
  # Force sequential execution when running tests on iOS devices.
  if ios_device:
    lit_config.warning('Forcing sequential execution for iOS device tests')
    lit_config.parallelism_groups['ios-device'] = 1
    config.parallelism_group = 'ios-device'

  # Only run up to 3 processes that require shadow memory simultaneously on
  # 64-bit Darwin. Using more scales badly and hogs the system due to
  # inefficient handling of large mmap'd regions (terabytes) by the kernel.
  else:
    lit_config.warning('Throttling sanitizer tests that require shadow memory on Darwin')
    lit_config.parallelism_groups['shadow-memory'] = 3

This is already the standard to configure the first part:

if not config.parallelism_group:
  config.parallelism_group = 'shadow-memory'

Except for unit tests (which don't have an explicit arch and just compile for the host), so we had a special callback to derive the arch from the test name. Since we don't need to distinguish between 32/64-bit anymore, we can just remove this part.

[delcypher]

LGTM

compiler-rt/test/asan/Unit/lit.site.cfg.py.in

65

Thanks for explaining.

compiler-rt/test/asan/Unit/lit.site.cfg.py.in

if config.enable_per_target_runtime_dir and config.target_arch != config.host_arch:
     if config.target_arch == 'i386':
         config.compiler_rt_libdir = re.sub(r'/x86_64(?=-[^/]+$)', '/i386', config.compiler_rt_libdir)
     elif config.target_arch == 'x86_64':
         config.compiler_rt_libdir = re.sub(r'/i386(?=-[^/]+$)', '/x86_64', config.compiler_rt_libdir)
 
 # Set LD_LIBRARY_PATH to pick dynamic runtime up properly.
 push_ld_library_path(config, config.compiler_rt_libdir)
 
-if config.host_os == 'Darwin':
-  config.parallelism_group = config.darwin_sanitizer_parallelism_group_func
+if not config.parallelism_group:
+  config.parallelism_group = 'shadow-memory'

compiler-rt/test/lit.common.cfg.py

if platform.system() == 'Darwin':
   if ios_device:
     lit_config.warning('Forcing sequential execution for iOS device tests')
     lit_config.parallelism_groups['ios-device'] = 1
     config.parallelism_group = 'ios-device'
 
   # Only run up to 3 processes that require shadow memory simultaneously on
   # 64-bit Darwin. Using more scales badly and hogs the system due to
   # inefficient handling of large mmap'd regions (terabytes) by the kernel.
-  elif config.target_arch in ['x86_64', 'x86_64h']:
-    lit_config.warning('Throttling sanitizer tests that require shadow memory on Darwin 64bit')
+  else:
+    lit_config.warning('Throttling sanitizer tests that require shadow memory on Darwin')
     lit_config.parallelism_groups['shadow-memory'] = 3
 
 # Multiple substitutions are necessary to support multiple shared objects used
 # at once.
 # Note that substitutions with numbers have to be defined first to avoid
 # being subsumed by substitutions with smaller postfix.
 for postfix in ["2", "1", ""]:
   if config.host_os == 'Darwin':

compiler-rt/test/sanitizer_common/Unit/lit.site.cfg.py.in

 @LIT_SITE_CFG_IN_HEADER@
 
 # Load common config for all compiler-rt unit tests.
 lit_config.load_config(config, "@COMPILER_RT_BINARY_DIR@/unittests/lit.common.unit.configured")
 
 # Setup config name.
 config.name = 'SanitizerCommon-Unit'
 
 # Setup test source and exec root. For unit tests, we define
 # it as build directory with sanitizer_common tests.
 # FIXME: De-hardcode this path.
 config.test_exec_root = os.path.join("@COMPILER_RT_BINARY_DIR@", "lib",
                                      "sanitizer_common", "tests")
 config.test_source_root = config.test_exec_root
 
-if config.host_os == 'Darwin':
-  config.parallelism_group = config.darwin_sanitizer_parallelism_group_func
+if not config.parallelism_group:
+  config.parallelism_group = 'shadow-memory'

compiler-rt/test/tsan/Unit/lit.site.cfg.py.in

 @LIT_SITE_CFG_IN_HEADER@
 
 # Load common config for all compiler-rt unit tests.
 lit_config.load_config(config, "@COMPILER_RT_BINARY_DIR@/unittests/lit.common.unit.configured")
 
 # Setup config name.
 config.name = 'ThreadSanitizer-Unit'
 
 # Setup test source and exec root. For unit tests, we define
 # it as build directory with ASan unit tests.
 # FIXME: De-hardcode this path.
 config.test_exec_root = "@COMPILER_RT_BINARY_DIR@/lib/tsan/tests"
 config.test_source_root = config.test_exec_root
 
-if config.host_os == 'Darwin':
-  config.parallelism_group = config.darwin_sanitizer_parallelism_group_func
+if not config.parallelism_group:
+  config.parallelism_group = 'shadow-memory'
 
+if config.host_os == 'Darwin':
   # On Darwin, we default to ignore_noninstrumented_modules=1, which also
   # suppresses some races the tests are supposed to find.  See tsan/lit.cfg.py.
   if 'TSAN_OPTIONS' in config.environment:
     config.environment['TSAN_OPTIONS'] += ':ignore_noninstrumented_modules=0'
   else:
     config.environment['TSAN_OPTIONS'] = 'ignore_noninstrumented_modules=0'
   config.environment['TSAN_OPTIONS'] += ':ignore_interceptors_accesses=0'

compiler-rt/unittests/lit.common.unit.cfg.py

if config.host_os == 'Darwin':
   # Only run up to 3 processes that require shadow memory simultaneously on
   # 64-bit Darwin. Using more scales badly and hogs the system due to
   # inefficient handling of large mmap'd regions (terabytes) by the kernel.
   lit_config.parallelism_groups["shadow-memory"] = 3
   # Disable libmalloc nanoallocator due to crashes running on macOS 12.0.
   #
   # rdar://80086125
   config.environment['MallocNanoZone'] = '0'
-
-  # The test config gets pickled and sent to multiprocessing workers, and that
-  # only works for code if it is stored at the top level of some module.
-  # Therefore, we have to put the code in a .py file, add it to path, and import
-  # it to store it in the config.
-  import site
-  site.addsitedir(os.path.dirname(__file__))
-  import lit_unittest_cfg_utils
-  config.darwin_sanitizer_parallelism_group_func = \
-    lit_unittest_cfg_utils.darwin_sanitizer_parallelism_group_func

compiler-rt/unittests/lit_unittest_cfg_utils.py

-# Put all 64-bit tests in the shadow-memory parallelism group. We throttle those
-# in our common lit config (lit.common.unit.cfg.py).
-def darwin_sanitizer_parallelism_group_func(test):
-  return "shadow-memory" if "x86_64" in test.file_path else None