[test] Stressing random seed with multiple subtests in parallel

Bug: v8:6917
Change-Id: I562680ebbc4b3140fb0e5be7cab7d5ebb658bbac
Reviewed-on: https://chromium-review.googlesource.com/893272Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Commit-Queue: Michał Majewski <majeski@google.com>
Cr-Commit-Position: refs/heads/master@{#50989}

tools/testrunner/standard_runner.py

@@ -633,9 +633,10 @@ class StandardTestRunner(base_runner.BaseTestRunner):
       return exit_code
 
     def _create_seed_proc(self, options):
-      if options.random_seed_stress_count == 1 and options.random_seed:
+      if options.random_seed_stress_count == 1:
         return None
-      return SeedProc(options.random_seed_stress_count, options.random_seed)
+      return SeedProc(options.random_seed_stress_count, options.random_seed,
+                      options.j * 4)
 
     def _create_rerun_proc(self, ctx):
       if not ctx.rerun_failures_count:

tools/testrunner/testproc/seed.py

@@ -10,17 +10,22 @@ from ..utils import random_utils
 
 
 class SeedProc(base.TestProcProducer):
-  def __init__(self, count, seed=None):
+  def __init__(self, count, seed=None, parallel_subtests=1):
     """
     Args:
       count: How many subtests with different seeds to create for each test.
         0 means infinite.
       seed: seed to use. None means random seed for each subtest.
+      parallel_subtests: How many subtest of each test to run at the same time.
     """
     super(SeedProc, self).__init__('Seed')
     self._count = count
     self._seed = seed
     self._last_idx = defaultdict(int)
+    self._todo = defaultdict(int)
+    self._parallel_subtests = parallel_subtests
+    if count:
+      self._parallel_subtests = min(self._parallel_subtests, count)
 
   def setup(self, requirement=base.DROP_RESULT):
     super(SeedProc, self).setup(requirement)
@@ -29,9 +34,11 @@ class SeedProc(base.TestProcProducer):
     assert requirement == base.DROP_RESULT
 
   def _next_test(self, test):
-    self._try_send_next_test(test)
+    for _ in xrange(0, self._parallel_subtests):
+      self._try_send_next_test(test)
 
   def _result_for(self, test, subtest, result):
+    self._todo[test.procid] -= 1
     self._try_send_next_test(test)
 
   def _try_send_next_test(self, test):
@@ -43,7 +50,9 @@ class SeedProc(base.TestProcProducer):
     if not self._count or num < self._count:
       num += 1
       self._send_test(create_subtest(num))
+      self._todo[test.procid] += 1
       self._last_idx[test.procid] = num
-    else:
+    elif not self._todo.get(test.procid):
       del self._last_idx[test.procid]
+      del self._todo[test.procid]
       self._send_result(test, None)