C/C++ Eclipse Project Generation

With the landing of bug 973770 (and a few touch up landing this week) the Mozilla build system can now generate a fully working out-of-the-box no hassle eclipse workspace for C++ gecko development. This has been tested for Mac, Fennec and B2G. For Windows please use the Visual Studio project generator. If you find any bugs please file and link off bug 973770.

Didn’t we already support eclipse projects? Yes we did but the setup was quite tedious to setup and maintain. My approach automates some of these instructions and uses the information now available from within moz.build to generate the project. This also means we can remove the build scanning phase which tends to make Eclipse unresponsive.

To use this:

  • Download the latest Eclipse CDT 8.3 package for your platform
  • Build your tree
  • Run |./mach build-backend -b CppEclipse|. For b2g cd into objdir-gecko and use |../gecko/mach build-backend -b CppEclipse|
  • Start eclipse, use $OBJDIR/eclipse_workspace as the workspace
  • File->Import->Existing Project with path $OBJDIR/eclipse_workspace/gecko
  • Let the indexer run on the first start. This can take about 20 mins (long but worth it, see below). This will index your exact mozconfig setup (example -DDEBUG, b2g system libs).

Here are some benefits:


Code Completion

Call Hierarchy

Call Hierarchy

Build, Flash (b2g), Launch

Build, Flash (b2g), Launch

Type Hierarchy

Type Hierarchy

Mozilla Formatter

Mozilla Formatter

If you find yourself tweaking the project let me know so that I can integrate changes into the project generator instead where everyone can benefit.


Introducing Scroll-Graph

For awhile I’ve been warning people that the FPS counter is very misleading. There’s many case where the FPS might be high but the scroll may still not be smooth. To give a better indicator of the scrolling performance I’ve written Scroll-Graph which can be enabled via layers.scroll-graph. Currently it requires OMTC+OGL but if this is useful we can easily port this to OMTC+D3D. Currently it works best on Desktop, it will need a bit more work for mobile to be compatible with APZC.

To understand how Scroll-Graph works lets look at scrolling from the point of view of a¬†physicist. Scrolling and pan should be smooth. The ideal behavior is for scrolling to behave like you have a page on a low friction surface. Imagine that the page is on a low friction ice arena and that every time you fling the page with your finger or the trackpad you’re applying force to the page. The friction of the ice is applying a small force in the opposite direction. If you plot the velocity graph you’d expect to see something like this roughly:

Expected Velocity Graph

Expected Velocity Graph

Now if we scroll perfectly then we expect the velocity of a layer to follow a similar curve. The important part is *not* the position of the velocity curve but it’s the smoothness of the velocity graph. Smooth scrolling means the page has a smooth velocity curve.

Now on to the fun part. Here’s some examples of Scroll-Graph in the browser. Here’s I pan a page and get smooth scrolling with 2 minor inperfections (Excuse the low FPS gif, the scrolling was smooth):

Smooth ScrollGraph velocity = Smooth Scrolling

Smooth ScrollGraph velocity = Smooth Scrolling

Now here’s an example of a jerky page scrolling. Note the Scroll-Graph is not smooth at all but very ‘spiky’ and it was noticeable to the eye:

Jerky scrolling = Jerky Scroll-Graph

Jerky scrolling = Jerky Scroll-Graph

Better Visual Studio Projects

I just wanted to add to Vlad’s post and show the current progress of generating the Visual Studio Project made this weekend by Vlad and I.

By using the approach mentioned in Vlad’s post we can target Visual Studio directly instead of a build system like Ninja. This gives Visual Studio the correct build flags for each file allowing features like IntelliSense and building from Visual Studio using MSBuild to work perfectly. I’m generating a project per shared library and a Visual Studio solution to group the results together. The results are quite neat because it shows at a glance which sources files are included in each library. Any files listed in the visual studio project are safe to edit which should cover the common developer workflow of editing cpp/headers and recompiling. Other rarer changes for platform developers like adding a new file and tweaking build settings should be done by closing visual studio, doing a local change and rebuilding with the mozilla build system and re-openning the updated Visual Studio Solution.

Visual Studio Build

Visual Studio IntelliSense + Build

This isn’t ready for general use yet because we still don’t generate the Link step properly and handle some corner cases in XUL yet but simpler libraries like gkmedias.dll is already working well. Supporting XUL should only require a few days of work. Once this is fixed we can move to supporting advanced Visual Studio features like “Edit and Continue” and distributed compiling.

Profiler @ Snappy Work Week

Last week I attended the snappy work week with goal of syncing up with Julian Seward and Mike Hommey regarding the new Breakpad unwinding feature, planning and prioritizing new feature work. I also got lots of valuable feedback. Here’s what you need to know if you’re a frequent user of the Gecko Profiler.

Breakpad Unwinding (Mobile)

For the last few months Julian has been spearheading integrating the breakpad unwinding feature to the Gecko Profiler. This turned out to be a very complicated task because we’re trying to use Breakpad for something it wasn’t meant to do. This work is now landed but it only works in a very specific build configuration (unwind tables, unpacking the libraries, no elfhack). We are currently working on addressing these problems to make it work in the default Nightly configuration.

Our current target is to use Breakpad unwinding in the Linux May 1st nightly. A week later have the Fennec nightly support breakpad unwinding. I’m hoping afterwards to support Breakpad unwinding on B2G central (not b2g18) but I expect this may be difficult on a memory constraint phone so I currently have no estimate for this at this time.

If you looked at the code for the profiler you may notice TableTicker1+TableTicker2. During the work week we refactored the code significantly to address this code duplication while resolving inconsistencies between the frame-pointer unwinder and the Breakpad unwinder.

Multi-Thread/Multi-Process Support

The profiler will soon support showing samples and timelines for multiple threads. This is already somewhat supported on B2G if you use a script written by Vlad. This will become easier as we begin to add multi-thread support to all the platform backends (already in progress for Mac and Linux) thanks to the help of James Willcox. This ties in heavily with the next two section (IPDL/Plugins).

Plugin Support

Plugin issues have long been identified as the single biggest contributor to responsiveness issues by Vladan‘s Chrome Hang work. This was the topic of the break out discussion headed by Benjamin Smedberg. We discussed a plan of attack by adding profiling to the plugin process which should land this week but require a manual step. This feature will let us know what’s going on in the plugin process when the browser’ main thread is waiting for an IPC response (and vice versa). It will improve as we add profiling support for profiling IPDL messages.

Flash Profiling

Flash initializing audio on plugin-container startup.

IPDL Message Support

During the week we decided to add profiler labels to each IPDL call automatically. That will help where the unwinder isn’t supported but doesn’t give us the data we need. In particular we’re looking to get better data about how IPDL messages are queued, how long they take to get dequeued and to processed. Combined with the Plugin support this should help us diagnose complex issues with our plugin-container or get better data on how particular plugins are hurting the responsiveness of the browser. Georg Fritzsche has an excellent plan in bug 853864 on how to implement this.

Shutdown Reporter Results

In a previous blog post I asked for volunteers to send in their shutdown profiles automatically. I’ve received hundreds of slow shutdown profiles, 30 profiles of which are over 10 seconds and one as high as 80 seconds! These profiles show us where Firefox is spending its time when closing down to the millisecond.

Before I started this experiment I asked around for what people thought was the cause of the slow shutdowns. The overwhelming response I got was that it was Garbage Collection and Cycle Collection. While those operations do make the shutdowns slower, they were rarely responsible for those 10 to 80 seconds shutdown times.

Here’s some interesting issues we found:

  • A few start-up optimizations moved operations off the startup path and into timers that would update the startup cache, or load fonts. These timers were never canceled when shutting down so they would lead to things such as font loading while shutting down. Since you have to open & close the browser within a minute to see these issues they are not critical for our users but these are certainly bugs we are cleaning up. Keep in mind if you are running timers you should stop them on shutdown before they fire if they are no longer useful.
  • On a related note we have timers going off during the shutdown. Particularly GC and CC timers. There is no guarantee that the shutdown will take long enough for these timers to run. If these are useless then we will waste time but if they are important they may not run.
  • Stopping plug-ins can take up to a second. I do not capture what is happening in the plug-in process so I can’t tell if it’s our container or the plug-in.
  • Releasing style sheets on shutdown will sometimes total over 1 second of execution on slow shutdown.
  • Time spent in sqlite3close in some profiles is as high as 10 seconds.
  • Bookmark backups are hurting us.
Shutdown metrics

Shutdown metrics

A big thumbs up to people who are submitting shutdown profiles. The data we are collecting is very valuable in helping us understand how Firefox behaves outside the labs.

Is Your Shutdown Slow? Turn On The Performance Reporter!

Does your Firefox take a long time to shutdown? Do you get “Firefox is already running” messages when restarting? Well the Firefox Performance team would like to fix that, so please keep reading!

The Gecko Profiler extension now has a new feature called the (Automatic) ‘Performance Reporter’. If you opt into this feature, the profiler will watch your browser for any performance hiccups and will automatically send a detailed bug report for the Performance team to fix! Currently, this Performance Reporter feature monitors only your browser’s shutdown behavior and only sends us a report if shutdown takes longer then 1.5 seconds, but we would like to extend it to cover all aspects of Firefox performance. The reporter works in the background and does not interfere with your use of the browser.

The performance reports contain the URLs of the tabs you have open and are uploaded publicly for processing, so if you are not comfortable with communicating this information, do not enable this feature — we understand! We have taken precautions to never record anything coming from a private browsing window. Also, please note that the Performance Reporter is not related to Firefox’s Telemetry or Health Report features which never send any sensitive information such as URLs. The Performance Reporter is different — it collects very rich data so we can get a complete picture of any performance problem.

How do you turn this on? Make sure you’re running the latest version of the Gecko Profiler which should read as v1.11.17 or later. If I have not scared you away great, turning on the Performance Reporter is as simple as flipping ‘profiler.performanceReporter’ in about:config.

Analyzing page load performance frame-by-frame

We’ve previously added video profiles in mobile and run them daily with eideticker. Here’s a proof a concept for doing the same thing for tracking page load on desktop.

This works by tagging frames and CPU samples with a frame number. During the analysis we use this information to correlate the video stream with the CPU samples. This lets us take something like a page load, slow it down and watch what we’re executing at each frame.

Take a look at this profile and follow along. I’ll only describe 4 interesting frames but feel free to look at the rest. When seeking with the video the corresponding region will be highlighted in the profile timeline. You can then click on samples in that timeline and they will be selected and appear as green:

  • Seek to 4 seconds where the page is requested. This will continue to 5.5 seconds. During this we see a little network activity and a bit of work compositing to update the throbber. This is no surprise since my WiFi signal was poor.
  • Seek to 5.5 seconds where the page starts to appear on screen. Lets look closer at the first frame in order.
    1. 20 ms compiling JS
    2. 8 ms executing the JS from the page
    3. 5 ms is spent in Adblock
    4. 11 ms processing styles
    5. 37 ms reflowing the page, 16 ms of which is doing main thread IO loading fonts when calling ‘CGFontCreateWithFontName’.
    6. Negligible time building the display list (profiler sampling rate too high)
    7. 19 ms drawing and compositing
  • Seek to 5.9 seconds where we are waiting on the plugin to load. The plugin takes 200ms to load. This means we miss several frames.
  • Seek to about 7.3 seconds. During this frame the plugin stream is created. This adds another 100 ms delay.
Video Profile of Page Load

Video Profile of Page Load

My goal is to start making video capture features into the profiler add-on to make these profiles easier to capture.