Profiling with the gecko profiler

Good at: Native stacks (with runtime options) + javascript profiling, low overhead sampling, familiar for gecko developers

See these instructions. Patches are in-flight to get native stacks in profiles, but that's not in default configurations yet.

Profiling with systrace

Good at: Shows process preemption, shows all calls to instrumented functions, Familiar for android developers

Bad at: Requires configure option, higher overhead

• Download android sdk to get systrace tool:
  • 1. download link
  • 2. the systrace.py tool is at path-to-android-sdk/tools/systrace

• Enable systrace in B2G:
  • Build with '--enable-systrace' config or just uncomment the MOZ_USE_SYSTRACE define in gecko/tools/profiler/GeckoProfilerImpl.h like:

#define MOZ_USE_SYSTRACE
#ifdef MOZ_USE_SYSTRACE
# define ATRACE_TAG ATRACE_TAG_ALWAYS
// We need HAVE_ANDROID_OS to be defined for Trace.h.
// If its not set we will set it temporary and remove it.
# ifndef HAVE_ANDROID_OS
#   define HAVE_ANDROID_OS
#   define REMOVE_HAVE_ANDROID_OS
# endif

• How to use systrace:
  • systrace.py document
  • ./systrace.py --time=10 -o mynewtrace.html sched

Note: Gecko code is tagged as ATRACE_TAG_ALWAYS, so we don't set the category type.