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Profiling Chromium and Blink

There are a few ways to profile Chromium and Blink.  Here are some of the tools that work well for diagnosing performance problems.
See also the Deep memory profiler.

Built-In Tools

For JavaScript issues, the built in profiler works very well.  To use this open up the Chrome Dev Tools (right click, Inspect Element) and select the 'Profiles' tab.

For a broader understanding of Chromium speed and bottlenecks, as well as understanding how posted-task and threads interact in aggregate, there is a cross-platform, task-level profiler built in.  Profiler results can be seen in about:profiler (or equivalently chrome://profiler)  For more details, visit  (http://www.chromium.org/developers/threaded-task-tracking).

See chrome://tracing for timelines showing TRACE_EVENT activity across all the different threads; originally used for GPU performance, and will probably require you to add TRACE_EVENT calls to the features you're interested in outside of compositing & rendering (this was named about://gpu through M14).

C++

For native C++ code the tools depend on the OS.
Note that basic printf debugging and using a general debugger (such as gdb) may be sufficient for some purposes. However, more specialized tools are available.

Linux, ChromeOS, Android

See https://chromium.googlesource.com/chromium/src/+/master/docs/profiling.md

OS X

DTrace and the pre-packaged "CPU Sampler" tool in Xcode work well.  Shark or the command-line sample work also, though they both will spend an exceedingly long time processing symbols if you are running Leopard (10.5).  Anecdotally this is much faster in Snow Leopard (10.6)

Windows

SyzyProf is a made-to-order, license-free, instrumenting hierarchical performance profiler that works well with Chrome. The aim with SyzyProf is to allow comprehensive profiling of Chrome code, including profiling over tasks or IPC, as well as integrated profiling over JavaScript in V8 and C++. SyzyProf is implemented as a 20% labor of love by a small group of Chrome developers, and we're looking for more >= 20% help.

Visual Studio also includes an instrumenting profiler. "vsinstr /help" and "vsperfcmd /help" have details for additional options. Currently this requires a non-debug non-component build of Chromium (debug or component builds omit the /profile linker flag).

Windows Performance Toolkit (WPT) is a free profiler from Microsoft that can profile CPU consumption, CPU idle time, file I/O, disk I/O, and more. To use WPT you need Windows 7 or higher. Getting started instructions for recording a trace using wprui can be found on this blog post. To record a trace just follow steps 1, 5, and 6. Trace analysis can then be done (be sure to configure Chrome's symbol server) or the trace can be shared on Google drive by analysis by somebody else.

I've heard that Purify has a profiler but have no experience with this personally.

AMD Code Analyst is a free profiler that can run inside Visual Studio. It captures frequency counts for functions in every process on the computer. It can optionally capture call-stack information, %CPU, and memory usage statistics; even with the Frame Pointer Omission optimization turned off (build\internal\release_defaults.gypi; under 'VCCLCompilerTool' set 'OmitFramePointers':'false'?), the call stack capture can have lots of bad information, but at least the most-frequent-caller seems accurate in practice.

Intel's VTune 9.1 does work in the Sampling mode (using the hardware performance counters), but call graphs are unavailable in Windows 7/64.  Note also that drilling down into the results for chrome.dll is extremely slow (on the order of many minutes) and may appear hung.  It does work (I suggest coffee or foosball).  VTune has been essentially supplanted by Intel® VTune™ Amplifier XE, which is an entirely new code base and interface, AFAIK.

Very Sleepy (http://www.codersnotes.com/sleepy) is a light-weight standalone profiler that seems to works pretty well for casual use and offers a decent set of features.

Android

See Profiling Content Shell on Android for detailed Android-specific instructions, and Telemetry profiling for general instructions about using Telemetry to profile (rather than using adb_profile_chrome).

GPU profiling
Both nVidia PerfHUD and Microsoft PIX are freely available. They may not run without making minor changes to how the graphics contexts are set up; check with the chrome-gpu team for current details.

The OpenGL Profiler for OSX allows real-time inspection of the top GL performance bottlenecks, as well as call traces.  In order to use it with Chrome/Mac, you must pass --disable-gpu-sandbox on the command line.  Some people have had more luck attaching it to the GPU process after-the-fact than launching Chrome from within the Profiler; YMMV.

GPUView is a Windows tool that utilizes ETW (Event Tracing for Windows) for visualizing low-level GPU, driver and kernel interactions in a time-based viewer.  It's available as part of the Microsoft Windows Performance Toolkit, in  %ProgramFiles%\Windows Kits\8.1\Windows Performance Toolkit\GPUView.  There's a README.TXT in there with basic instructions, or see http://graphics.stanford.edu/~mdfisher/GPUView.html. Traces for loading into GPUView can be recorded with wprui (see the Windows section).
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