Enabling Just-in-Time Recompilation on Droid Incredible

This modification will enable Just-in-Time recompilation (JIT) on Android 2.1 on the Droid Incredible. JIT is a technique that makes interpreted programming languages, like the Dalvik VM that Android applications are programmed in, run faster. Advanced users may want to experiment with enabling JIT to increase responsiveness and performance on their phones.

Prerequisites

To apply this modification:

  • Your phone must be rooted.
  • Your phone must have a custom recovery image installed. This can be accomplished with unrevoked2.
  • You must disable the Sense launcher and install a custom launcher.
  • You must disable the Sense lockscreen.
  • Thus, it is recommended that you run a custom ROM with Sense disabled entirely.
  • Your phone must not have any of the known-incompatible applications on it. These applications include:
    • Pandora
    • XDA Application
    • The HTC Sense Launcher

Instructions

Perform the following steps to enable JIT recompilation on your phone.

  1. Before making any changes to your phone, always run a nandroid backup from recovery.
  2. Optionally, install Linpack on your phone from the Android Market. Linpack is a benchmark that allows you to determine how fast Dalvik VM code is running on your phone. Run it before enabling JIT to get a baseline measurement of your phone's performance.
  3. Download this ZIP file (credit to gr0gmint from XDA). Unzip it to a location that you can get to with adb.
  4. Reboot the phone into recovery mode.
  5. Select “Partitions” from the ClockworkMod menu, and select “mount /system”.
  6. Run adb pull /system/build.prop build.prop and edit the file.
    1. Add the following line:
      dalvik.vm.execution-mode=int:jit
    2. Modify this line:
      dalvik.vm.heapsize=24m

      to read as follows:

      dalvik.vm.heapsize=38m
  7. Send the new files to the phone by running the following commands:
    1. adb push build.prop /system/build.prop
    2. adb push libdvm.so /system/lib
    3. adb push libnativehelper.so /system/lib
    4. adb push dalvikvm /system/bin
  8. Start an adb shell, and run the following commands:
    1. chmod 0755 /system/bin/dalvikvm
    2. chmod 0644 /system/lib/libdvm.so
    3. chmod 0644 /system/lib/libnativehelper.so
    4. umount /system
    5. exit
  9. From the ClockworkMod menu, select the “Wipe cache partition” option, and reboot.
  10. If you installed Linpack before, run it again now. You should see a noticeable improvement in your device's Linpack score.
  11. To confirm that JIT is enabled, run adb shell getprop dalvik.vm.execution-mode. It should return int:jit

Important information

This software is offered to you with NO WARRANTY, either express or implied. By downloading it, you accept the full and ultimate responsibility for any consequences of using it.

 
public/how_to_enable_jit.txt · Last modified: 2010/07/07 12:49 by rpearl
 
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