--- a/taskcluster/ci/test/misc.yml
+++ b/taskcluster/ci/test/misc.yml
@@ -200,8 +200,47 @@ test-coverage:
                     - unittests/linux_unittest.py
                     - remove_executables.py
                 macosx.*:
                     - unittests/mac_unittest.py
                 windows.*:
                     - unittests/win_taskcluster_unittest.py
         extra-options:
             - --per-test-coverage
+
+test-coverage-gpu:
+    description: "Per-test coverage for tests that require gpu instances"
+    suite: test-coverage
+    treeherder-symbol: TCg
+    loopback-video: true
+    virtualization: virtual-with-gpu
+    instance-size: default
+    max-run-time: 10800
+    allow-software-gl-layers: false
+    run-on-projects:
+        by-test-platform:
+            # only run on mozilla-central and try.
+            .*-ccov/.*: ['mozilla-central', 'try']
+            default: []
+    tier:
+        by-test-platform:
+            windows10-64-asan.*: 3
+            default: 2
+    mozharness:
+        script:
+            by-test-platform:
+                android.*: android_emulator_unittest.py
+                default: desktop_unittest.py
+        config:
+            by-test-platform:
+                android.*:
+                    - android/android_common.py
+                    - android/androidarm_4_3.py
+                linux.*:
+                    - unittests/linux_unittest.py
+                    - remove_executables.py
+                macosx.*:
+                    - unittests/mac_unittest.py
+                windows.*:
+                    - unittests/win_taskcluster_unittest.py
+        extra-options:
+            - --per-test-coverage
+            - --gpu-required

--- a/taskcluster/taskgraph/util/perfile.py
+++ b/taskcluster/taskgraph/util/perfile.py
@@ -14,18 +14,19 @@ from subprocess import CalledProcessErro
 from taskgraph import files_changed
 from .. import GECKO
 
 logger = logging.getLogger(__name__)
 
 
 @memoize
 def perfile_number_of_chunks(try_task_config, head_repository, head_rev, type):
-    # TODO: Make this flexible based on coverage vs verify || test type
     tests_per_chunk = 10.0
+    if type.startswith('test-coverage'):
+        tests_per_chunk = 30.0
 
     if type.startswith('test-verify-wpt') or type.startswith('test-coverage-wpt'):
         file_patterns = ['testing/web-platform/tests/**',
                          'testing/web-platform/mozilla/tests/**']
     elif type.startswith('test-verify-gpu') or type.startswith('test-coverage-gpu'):
         file_patterns = ['**/*webgl*/**/test_*',
                          '**/dom/canvas/**/test_*',
                          '**/gfx/tests/**/test_*',

--- a/testing/mozharness/mozharness/mozilla/testing/per_test_base.py
+++ b/testing/mozharness/mozharness/mozilla/testing/per_test_base.py
@@ -87,45 +87,47 @@ class SingleTestMixin(object):
             self.info("Per-test run updated with manifest %s" % path)
 
         # for each changed file, determine if it is a test file, and what suite it is in
         for file in changed_files:
             # manifest paths use os.sep (like backslash on Windows) but
             # automation-relevance uses posixpath.sep
             file = file.replace(posixpath.sep, os.sep)
             entry = tests_by_path.get(file)
-            if entry:
-                if gpu and entry[1] not in ['gpu', 'webgl']:
-                    continue
-                elif not gpu and entry[1] in ['gpu', 'webgl']:
-                    continue
+            if not entry:
+                continue
+
+            if gpu and entry[1] not in ['gpu', 'webgl']:
+                continue
+            elif not gpu and entry[1] in ['gpu', 'webgl']:
+                continue
 
-                self.info("Per-test run found test %s" % file)
-                subsuite_mapping = {
-                    ('browser-chrome', 'clipboard'): 'browser-chrome-clipboard',
-                    ('chrome', 'clipboard'): 'chrome-clipboard',
-                    ('plain', 'clipboard'): 'plain-clipboard',
-                    ('browser-chrome', 'devtools'): 'mochitest-devtools-chrome',
-                    ('browser-chrome', 'screenshots'): 'browser-chrome-screenshots',
-                    ('plain', 'media'): 'mochitest-media',
-                    # below should be on test-verify-gpu job
-                    ('browser-chrome', 'gpu'): 'browser-chrome-gpu',
-                    ('chrome', 'gpu'): 'chrome-gpu',
-                    ('plain', 'gpu'): 'plain-gpu',
-                    ('plain', 'webgl'): 'mochitest-gl',
-                }
-                if entry in subsuite_mapping:
-                    suite = subsuite_mapping[entry]
-                else:
-                    suite = entry[0]
-                suite_files = self.suites.get(suite)
-                if not suite_files:
-                    suite_files = []
-                suite_files.append(file)
-                self.suites[suite] = suite_files
+            self.info("Per-test run found test %s (%s)" % (file, entry[0]))
+            subsuite_mapping = {
+                ('browser-chrome', 'clipboard'): 'browser-chrome-clipboard',
+                ('chrome', 'clipboard'): 'chrome-clipboard',
+                ('plain', 'clipboard'): 'plain-clipboard',
+                ('browser-chrome', 'devtools'): 'mochitest-devtools-chrome',
+                ('browser-chrome', 'screenshots'): 'browser-chrome-screenshots',
+                ('plain', 'media'): 'mochitest-media',
+                # below should be on test-verify-gpu job
+                ('browser-chrome', 'gpu'): 'browser-chrome-gpu',
+                ('chrome', 'gpu'): 'chrome-gpu',
+                ('plain', 'gpu'): 'plain-gpu',
+                ('plain', 'webgl'): 'mochitest-gl',
+            }
+            if entry in subsuite_mapping:
+                suite = subsuite_mapping[entry]
+            else:
+                suite = entry[0]
+            suite_files = self.suites.get(suite)
+            if not suite_files:
+                suite_files = []
+            suite_files.append(file)
+            self.suites[suite] = suite_files
 
     def _find_wpt_tests(self, dirs, changed_files):
         # Setup sys.path to include all the dependencies required to import
         # the web-platform-tests manifest parser. web-platform-tests provides
         # the localpaths.py to do the path manipulation, which we load,
         # providing the __file__ variable so it can resolve the relative
         # paths correctly.
         paths_file = os.path.join(dirs['abs_wpttest_dir'],
@@ -194,17 +196,17 @@ class SingleTestMixin(object):
             for c in contents['changesets']:
                 self.info(" {cset} {desc}".format(
                     cset=c['node'][0:12],
                     desc=c['desc'].splitlines()[0].encode('ascii', 'ignore')))
                 changed_files |= set(c['files'])
 
         if self.config.get('per_test_category') == "web-platform":
             self._find_wpt_tests(dirs, changed_files)
-        elif self.config.get('gpu_required'):
+        elif self.config.get('gpu_required', 'False') != 'False':
             self._find_misc_tests(dirs, changed_files, gpu=True)
         else:
             self._find_misc_tests(dirs, changed_files)
 
         # per test mode run specific tests from any given test suite
         # _find_*_tests organizes tests to run into suites so we can
         # run each suite at a time
 

--- a/testing/mozharness/scripts/desktop_unittest.py
+++ b/testing/mozharness/scripts/desktop_unittest.py
@@ -764,16 +764,18 @@ class DesktopUnittest(TestingMixin, Merc
         """run suite(s) to a specific category"""
         dirs = self.query_abs_dirs()
         suites = self._query_specified_suites(suite_category)
         abs_app_dir = self.query_abs_app_dir()
         abs_res_dir = self.query_abs_res_dir()
 
         max_per_test_time = timedelta(minutes=60)
         max_per_test_tests = 10
+        if self.per_test_coverage:
+            max_per_test_tests = 30
         executed_tests = 0
         executed_too_many_tests = False
 
         if suites:
             self.info('#### Running %s suites' % suite_category)
             for suite in suites:
                 if executed_too_many_tests and not self.per_test_coverage:
                     return False

--- a/testing/mozharness/scripts/web_platform_tests.py
+++ b/testing/mozharness/scripts/web_platform_tests.py
@@ -313,16 +313,18 @@ class WebPlatformTest(TestingMixin, Merc
         else:
             env['STYLO_THREADS'] = '4'
 
         env = self.query_env(partial_env=env, log_level=INFO)
 
         start_time = datetime.now()
         max_per_test_time = timedelta(minutes=60)
         max_per_test_tests = 10
+        if self.per_test_coverage:
+            max_per_test_tests = 30
         executed_tests = 0
         executed_too_many_tests = False
 
         if self.per_test_coverage or self.verify_enabled:
             suites = self.query_per_test_category_suites(None, None)
             if "wdspec" in suites:
                 # geckodriver is required for wdspec, but not always available
                 geckodriver_path = self._query_geckodriver()