How to update dirty-image-objects

1. Add imgdiag to ART APEX.

The easiest way is to modify art/build/apex/Android.bp like this:

 art_runtime_binaries_both = [
     "dalvikvm",
     "dex2oat",
+    "imgdiag",
 ]

2. Install ART APEX and reboot, e.g.:

m apps_only dist
adb install out/dist/com.android.art.apex
adb reboot

3. Collect imgdiag output.

# To see all options check: art/imgdiag/run_imgdiag.py -h

art/imgdiag/run_imgdiag.py

4. Create new dirty-image-objects.

# To see all options check: art/imgdiag/create_dirty_image_objects.py -h

# Using all imgdiag files:
art/imgdiag/create_dirty_image_objects.py ./imgdiag_*

# Or using only specified files:
art/imgdiag/create_dirty_image_objects.py \
  ./imgdiag_system_server.txt \
  ./imgdiag_com.android.systemui.txt \
  ./imgdiag_com.google.android.gms.txt \
  ./imgdiag_com.google.android.gms.persistent.txt \
  ./imgdiag_com.google.android.gms.ui.txt \
  ./imgdiag_com.google.android.gms.unstable.txt

5. Push new dirty-image-objects to the device.

adb push dirty-image-objects.txt /etc/dirty-image-objects

6. Reinstall ART APEX to update the boot image.

adb install out/dist/com.android.art.apex
adb reboot

At this point the device should have new boot.art with optimized dirty object layout. This can be checked by collecting imgdiag output again and comparing dirty page counts to the previous run.