diff --git a/etc/ci/performance/runner.py b/etc/ci/performance/runner.py
index ab5a31c4a6d0..a7014e24f285 100644
--- a/etc/ci/performance/runner.py
+++ b/etc/ci/performance/runner.py
@@ -43,6 +43,7 @@ def get_servo_command(url):
     ua_script_path = "{}/user-agent-js".format(os.getcwd())
     return ["../../../target/release/servo", url,
             "--userscripts", ua_script_path,
+            "--headless",
             "-x", "-o", "output.png"]
 
 
diff --git a/python/servo/testing_commands.py b/python/servo/testing_commands.py
index 88a6d7b24ca4..fdb471a437db 100644
--- a/python/servo/testing_commands.py
+++ b/python/servo/testing_commands.py
@@ -162,6 +162,8 @@ def suite_for_path(self, path_arg):
              description='Run the page load performance test',
              category='testing')
     def test_perf(self):
+        self.set_software_rendering_env(True)
+
         self.ensure_bootstrapped()
         env = self.build_env()
         return call(["bash", "test_perf.sh"],
@@ -422,31 +424,7 @@ def run_test_list_or_dispatch(self, requested_paths, correct_suite, correct_func
 
     # Helper for test_css and test_wpt:
     def wptrunner(self, run_file, **kwargs):
-        # On Linux and mac, find the OSMesa software rendering library and
-        # add it to the dynamic linker search path.
-        if sys.platform.startswith('linux'):
-            try:
-                args = [self.get_binary_path(kwargs["release"], not kwargs["release"])]
-                osmesa_path = path.join(find_dep_path_newest('osmesa-src', args[0]), "out", "lib", "gallium")
-                os.environ["LD_LIBRARY_PATH"] = osmesa_path
-                os.environ["GALLIUM_DRIVER"] = "softpipe"
-            except BuildNotFound:
-                # This can occur when cross compiling (e.g. arm64), in which case
-                # we won't run the tests anyway so can safely ignore this step.
-                pass
-        if sys.platform.startswith('darwin'):
-            try:
-                args = [self.get_binary_path(kwargs["release"], not kwargs["release"])]
-                osmesa_path = path.join(find_dep_path_newest('osmesa-src', args[0]),
-                                        "out", "src", "gallium", "targets", "osmesa", ".libs")
-                glapi_path = path.join(find_dep_path_newest('osmesa-src', args[0]),
-                                       "out", "src", "mapi", "shared-glapi", ".libs")
-                os.environ["DYLD_LIBRARY_PATH"] = osmesa_path + ":" + glapi_path
-                os.environ["GALLIUM_DRIVER"] = "softpipe"
-            except BuildNotFound:
-                # This can occur when cross compiling (e.g. arm64), in which case
-                # we won't run the tests anyway so can safely ignore this step.
-                pass
+        self.set_software_rendering_env(kwargs['release'])
 
         os.environ["RUST_BACKTRACE"] = "1"
         kwargs["debug"] = not kwargs["release"]
@@ -658,6 +636,33 @@ def dromaeo_test_runner(self, tests, release, dev):
         return check_call(
             [run_file, "|".join(tests), bin_path, base_dir])
 
+    def set_software_rendering_env(self, use_release):
+        # On Linux and mac, find the OSMesa software rendering library and
+        # add it to the dynamic linker search path.
+        if sys.platform.startswith('linux'):
+            try:
+                args = [self.get_binary_path(use_release, not use_release)]
+                osmesa_path = path.join(find_dep_path_newest('osmesa-src', args[0]), "out", "lib", "gallium")
+                os.environ["LD_LIBRARY_PATH"] = osmesa_path
+                os.environ["GALLIUM_DRIVER"] = "softpipe"
+            except BuildNotFound:
+                # This can occur when cross compiling (e.g. arm64), in which case
+                # we won't run the tests anyway so can safely ignore this step.
+                pass
+        elif sys.platform.startswith('darwin'):
+            try:
+                args = [self.get_binary_path(use_release, not use_release)]
+                osmesa_path = path.join(find_dep_path_newest('osmesa-src', args[0]),
+                                        "out", "src", "gallium", "targets", "osmesa", ".libs")
+                glapi_path = path.join(find_dep_path_newest('osmesa-src', args[0]),
+                                       "out", "src", "mapi", "shared-glapi", ".libs")
+                os.environ["DYLD_LIBRARY_PATH"] = osmesa_path + ":" + glapi_path
+                os.environ["GALLIUM_DRIVER"] = "softpipe"
+            except BuildNotFound:
+                # This can occur when cross compiling (e.g. arm64), in which case
+                # we won't run the tests anyway so can safely ignore this step.
+                pass
+
 
 def create_parser_create():
     import argparse