1076725 - Scrolling speed has become 200% slower after landing Bug 1044702 under condition of image.high_quality_downscaling.enabled = false & Direct2D

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Alice0775 White]

[Tracking Requested - why for this release]: significant perf regression

Under condition of image.high_quality_downscaling.enabled = false

Scrolling speed has become 200% slower after landing Bug 1044702.


Steps To Reproduce:
1. Set image.high_quality_downscaling.enabled = false
2. Open testcase index.html
   https://dl.dropboxusercontent.com/u/33246373/20140922031026.7z   
3. Run the following code in ScratchPad with chrome privilege

   (function() {
    function scroll(event) {
      var top = content.document.documentElement.scrollTop ||
               content.document.body.scrollTop;
      
      if (top < 11000) {
        var evt = content.document.createEvent("KeyboardEvent");
        evt.initKeyEvent ("keypress", true, true, window, 
                              null, null, null, null, 
                              40, 0) 
        content.document.dispatchEvent(evt)
      } else {
        content.removeEventListener("scroll", scroll, false);
        content.scrollTo(0,0);
        alert(new Date().getTime() - start);
      }
    }

    content.focus();
    content.scrollTo(0,0);
    var start = new Date().getTime();
    content.addEventListener("scroll", scroll, false);
    scroll();
})();

Actual Results:
The scrolling speed has become slow, 200% slow.

Regression window(m-i)
Good:
4500-5000 msec 
https://hg.mozilla.org/integration/mozilla-inbound/rev/80164e15bd54
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 ID:20140912024553
Bad:
14000-15000 msec 
https://hg.mozilla.org/integration/mozilla-inbound/rev/c232720a2847
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 ID:20140912025257

Pushlog: 
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=80164e15bd54&tochange=c232720a2847

Regressed by
 Bug 1044702 - Use Moz2D source clipping when we can. r=Bas

Comment 1

[Alice0775 White]

This was fixed by 1412188703 Bug 902952.