src/docs/profiling_content_shell_on_android.md

Profiling Content Shell on Android

Below are the instructions for setting up profiling for Content Shell on Android. This will let you generate profiles for ContentShell. This will require linux, building an userdebug Android build, and wiping the device.

[TOC]

Prepare your device.

You need an Android 4.2+ device (Galaxy Nexus, Nexus 4, 7, 10, etc.) which you don’t mind erasing all data, rooting, and installing a userdebug build on.

Get and build content_shell_apk for Android

More detailed insturctions in android_build_instructions.md.

ninja -C out/Release content_shell_apk

Setup the physical device

Plug in your device. Make sure you can talk to your device, try:

third_party/android_sdk/public/platform-tools/adb shell ls

Root your device and install a userdebug build

1. This may require building your own version of Android: http://source.android.com/source/building-devices.html
2. A build that works is: manta / android-4.2.2_r1 or master / full_manta-userdebug.

Root your device

1. Run adb root. Every time you connect your device you’ll want to run this.
2. If adb is not available, make sure to run . build/android/envsetup.sh

If you get the error error: device offline, you may need to become a developer on your device before Linux will see it. On Jellybean 4.2.1 and above this requires going to “about phone” or “about tablet” and clicking the build number 7 times: http://androidmuscle.com/how-to-enable-usb-debugging-developer-options-on-nexus-4-and-android-4-2-devices/

Enable profiling

Rebuild content_shell_apk with profiling enabled.

With GN:

gn args out/Profiling
# add "enable_profiling = true"
ninja -C out/Profiling content_shell_apk
export CHROMIUM_OUTPUT_DIR="$PWD/out/Profiling"

Run a Telemetry perf profiler

You can run any Telemetry benchmark with --profiler=perf, and it will:

1. Download perf and perfhost
2. Install on your device
3. Run the test
4. Setup symlinks to work with the --symfs parameter

You can also run "manual" tests with Telemetry, more information here: https://www.chromium.org/developers/telemetry/profiling#TOC-Manual-Profiling---Android

The following steps describe building perf, which is no longer necessary if you use Telemetry.

Use adb_profile_chrome

Even if you're not running a Telemetry test, you can use Catapult to automatically push binaries and pull the profile data for you.

build/android/adb_profile_chrome --browser=content_shell --perf

While you still have to build, install and launch the APK yourself, Catapult will take care of creating the symfs etc. (i.e. you can skip the "not needed for Telemetry" steps below).

Install /system/bin/perf on your device (not needed for Telemetry)

# From inside the Android source tree (not inside Chromium)
mmm external/linux-tools-perf/
adb remount # (allows you to write to the system image)
adb sync
adb shell perf top # check that perf can get samples (don’t expect symbols)

Install and Run ContentShell

Install with the following:

out/Release/bin/content_shell_apk run

If content_shell “stopped unexpectedly” use adb logcat to debug.

Setup a symbols directory with symbols from your build (not needed for Telemetry)

1. Figure out exactly what path content_shell_apk (or chrome, etc) installs to.

   • On the device, navigate ContentShell to about:crash

   adb logcat | grep libcontent_shell_content_view.so

You should find a path that’s something like /data/app-lib/org.chromium.content_shell-1/libcontent_shell_content_view.so

1. Make a symbols directory

   mkdir symbols (this guide assumes you put this next to src/)
   

2. Make a symlink from your symbols directory to your un-stripped content_shell.

   # Use whatever path in app-lib you got above
   mkdir -p symbols/data/app-lib/org.chromium.content_shell-1
   ln -s `pwd`/src/out/Release/lib/libcontent_shell_content_view.so \
       `pwd`/symbols/data/app-lib/org.chromium.content_shell-1
   

Install perfhost_linux locally (not needed for Telemetry)

Note: modern versions of perf may also be able to process the perf.data files from the device.

1. perfhost_linux can be built from: https://android.googlesource.com/platform/external/linux-tools-perf/.

2. Place perfhost_linux next to symbols, src, etc.

   chmod a+x perfhost_linux

Actually record a profile on the device!

Run the following:

out/Release/content_shell_apk ps (look for the pid of the sandboxed_process)
adb shell perf record -g -p 12345 sleep 5
adb pull /data/perf.data

Create the report

1. Run the following:

   ./perfhost_linux report -g -i perf.data --symfs symbols/
   

2. If you don’t see chromium/webkit symbols, make sure that you built/pushed Release, and that the symlink you created to the .so is valid!

Add symbols for the kernel

1. By default, /proc/kallsyms returns 0 for all symbols, to fix this, set /proc/sys/kernel/kptr_restrict to 0:

   adb shell echo “0” > /proc/sys/kernel/kptr_restrict
   

2. See http://lwn.net/Articles/420403/ for explanation of what this does.

   adb pull /proc/kallsyms symbols/kallsyms
   

3. Now add --kallsyms to your perfhost_linux command:

   ./perfhost_linux report -g -i perf.data --symfs symbols/ \
       --kallsyms=symbols/kallsyms