Snappy update for week of July 5th


Jared Wein discovered that our about:home was surprisingly expensive to load. He sped up the page by an estimated 30% in bug 765411. Similarly, Tim Taubert is fixing our new tab page performance in bug 753448.

Tim is also bravely attacking (via bug 769634) horrid performance issues with Firefox themes tracked by bug 650968.


Alex Crichton added ability to profile JS in bug 761261. Benoit Girard is adding labels to the profiler to expose JS profiling info in bug 707308.  Same functionality will also allow us to add URLs to the stacks. This means that in addition to seeing what Firefox is busy with, the profiler will now provide context on what caused the processing (screenshot). This is huge. Benoit also improved profiler timing data in 769989.

Slow Startup Research

As I mentioned before, Nicholas Chaim wrote an addon to track system IO usage while starting Firefox. He has since updated his addon to be hosted on AMO and to submit that data for analysis. If you suffer from slow Firefox startups, please help us identify common IO hogs by installing his addon. Please encourage friends with slow startups to do the same.

This addon lists names of processes and amount of IO they did. This is somewhat private information, we can’t gather this data via telemetry.


  1. Thanks Taras! Keep up the good work.

  2. Shortly before Flash 11.3 (stable) was released I started to notice a lot of jank/hangs when opening pages with several youtube flash video embeds.

    I’ve used the built in profiler in a nightly build to look at this, and have filed a bug here:

    With just D3D9 gpu accelerated composition most of the time is spent in KiFastSystemCallRet. With D2D/D3D10 (on a faster machine) most of the time was spent in NtWaitForMultipleObjects and NtUserWaitMessage).

    Hope this is of some use. 🙂



  3. Mikko Ohtamaa

    The new profiler looks awesomely useful!