Layout Test perf/clone-with-focus.html is a Flaky Failure

rniwa · rniwa · commit c6d1c81b9ee9 · 2019-08-22T05:51:53.000Z
https://bugs.webkit.org/show_bug.cgi?id=201012 Reviewed by Antti Koivisto. The flakiness was observed when the time to clone elements without focus is 0ms but the time to clone elements with focus is 1ms or greater. The test tries to make sure the time to clone elements with foucs is less than 2x of the time to clone elements without focus. When the time to clone without focus is 0ms, any difference is always more than 2x larger. Fixed the test by increasing the number of elements until the time to clone without focus takes at least 5ms. * perf/clone-with-focus.html: Canonical link: https://commits.webkit.org/214734@main git-svn-id: https://svn.webkit.org/repository/webkit/trunk@248996 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
@@ -1,3 +1,22 @@
+2019-08-21  Ryosuke Niwa  <rniwa@webkit.org>
+
+        Layout Test perf/clone-with-focus.html is a Flaky Failure
+        https://bugs.webkit.org/show_bug.cgi?id=201012
+
+        Reviewed by Antti Koivisto.
+
+        The flakiness was observed when the time to clone elements without focus is 0ms
+        but the time to clone elements with focus is 1ms or greater.
+
+        The test tries to make sure the time to clone elements with foucs is less than 2x
+        of the time to clone elements without focus. When the time to clone without focus
+        is 0ms, any difference is always more than 2x larger.
+
+        Fixed the test by increasing the number of elements until the time to clone without
+        focus takes at least 5ms.
+
+        * perf/clone-with-focus.html:
+
 2019-08-21  Myles C. Maxfield  <mmaxfield@apple.com>
 
         [WHLSL] Vertex shader and fragment shader need to be able to come from two different programs
diff --git a/LayoutTests/perf/clone-with-focus.html b/LayoutTests/perf/clone-with-focus.html
@@ -17,21 +17,22 @@
         {
             if (focusInput)
                 inputElement.focus();
-                
-            var startTime = Date.now();
+
+            var startTime = performance.now();
             for (var i = 0; i < numberOfElements; i++) {
                 var clone = templateElement.cloneNode(true);
                 clone.childNodes[0].textContent = i;
                 listElement.appendChild(clone);
             }
-            var endTime = Date.now();
-            
+            var endTime = performance.now();
+
             if (focusInput)
                 inputElement.blur();
-                
-            while (listElement.firstChild != listElement.lastChild)
-                listElement.removeChild(listElement.lastChild);
-            
+
+            const originalItem = listElement.firstChild;
+            listElement.textContent = '';
+            listElement.appendChild(originalItem);
+
             return endTime - startTime;
         }
 
@@ -42,8 +43,13 @@
             document.getElementById('console').appendChild(element);
         }
 
-        var timeWithoutFocus = test(1000, false);
-        var timeWithFocus = test(1000, true);
+        const start = performance.now();
+        let factor = 0;
+        while (test(1000 * factor, false) < 5)
+            factor++;
+
+        var timeWithoutFocus = test(1000 * factor, false);
+        var timeWithFocus = test(1000 * factor, true);
 
         if (Math.abs(timeWithFocus - timeWithoutFocus) <= timeWithoutFocus) {
             log('PASS. Cloning elements takes roughly as long with as without focus.');
