BBench-gem5

This page provides everything you need to get Android, and BBench, working on gem5. BBench is a new web-page rendering benchmark; you can read about it here: BBench. We have provided pre-compiled disk images and an Android kernel, as well as step-by-step instructions on how to get Android running on gem5 using the ARM ISA.

Running BBench on Android with gem5

Everything required to run BBench on gem5 is provided in the next section. You will need the kernel and the disk image (containing BBench).

1. Get gem5 from the Repository
2. Download the basic full system files from the Download page and build gem5 for the ARM ISA according to these instructions Compiling_M5
3. Point the M5_PATH environment variable to this location. E.g, type export M5_PATH=/path_to_gem5_system/system/
4. Download and uncompress the ARM/Android Kernel and place it in the /path_to_gem5_system/system/binaries directory
5. Download and uncompress the Android Disk Image and place it in the /path_to_gem5_system/system/disks directory
6. Run /path_to_gem5_root/build/ARM/m5.fast configs/example/fs.py -b bbench --kernel=vmlinux.smp.mouse.arm to run BBench on Android using ARM. Invoke from /path_to_gem5_root.

Note: These instructions and images are only for Android on the ARM ISA.

Android Full-System Files

These files contain everything you need to get Android, and BBench, up and running on gem5.

• 2.6.35 version kernel -- Pre-compiled Android kernel and config file.

• Gingergread Disk Image with BBench -- Disk image with a pre-compiled Android Gingerbread file system. This disk image contains all of the files generated during initial boot, as well as a self-terminating version of BBench and BusyBox.

• Clean Gingerbread Disk Image -- Disk image containing only the pre-compiled Android Gingerbread file system. This disk image contains no benchmarks and has never been booted.

• Clean ICS Disk Image -- Disk image containing only the pre-compiled Android ICS file system. The disk image contains no benchmarks and has never been booted.

Building Your Own Android File System and Kernel

This section gives step-by-step instructions for building a gem5 compatible Ice Cream Sandwich (ICS) disk image.

1. Initialize your build environment and download the Android source.
2. Get a copy of the Armdroid patches using the following command: git clone git://linux-arm.org/armdroid.git.
3. Copy the arm device files into the Android device folder: cp path_to_armdroid/fs/src/IceCreamSandwich/Android-ICS-device-arm.tar.bz2 path_to_android_src/device/. Then, untar it.
4. Copy the Armdroid patches to the appropriate Android source directory. These directories can be inferred from the patch file itself.
5. Apply those patches by changing to the directories in which the patches were copied and running the command: git apply *.patch
6. Change into the Android source root directory and build using: make PRODUCT-armboard_v7a-eng -jn.
7. Create a blank image using the gem5img.py utility: ./gem5img.py init android_ics_arm.img 1024
8. Create a mount point: sudo mkdir -p /mnt/ics
9. Mount the image: sudo mount -o loop,offset=32256 android_ics_arm.img /mnt/ics
10. Copy the root/ and system/ folders to the mounted image:
    1. cp -a path_to_android_src/out/target/product/armboard_v7a/root/* /mnt/ics
    2. cp -a path_to_android_src/out/target/product/armboard_v7a/system/* /mnt/ics/system
11. Unmount the image: sudo umount /mnt/ics

Now, to build the 2.6.35 kernel.

1. Get the kernel source: git clone git://linux-arm.org/linux-2.6-armdroid.git -b 2.6.35-armdroid
2. Get the 2.6.35 config file packaged with the linux kernel above.
3. Copy it to the kernel source directory as .config.
4. Build the kernel source: make ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- -jn vmlinux EXTRA_CFLAGS=-mno-unaligned-access

Note: these instructions assume you are using the arm-none-linux-gnueabi compiler toolchain from Sourcery CodeBench Lite.

Config file for 2.6.38 kernel coming soon.

Tips for Making Your Disk Image gem5 Friendly

Speeding Up the Boot Process

• When a fresh Android image is booted it generates a lot of files and does a lot of JIT compiling; this can slow down the boot process significantly. gem5 uses a copy-on-write (COW) layer between the simulator and the actual disk image, because of this COW layer none of the changes are stored to the disk image. To make these changes permanent, and avoid having to repeat them in the future, you can remove the COW during the first boot of an image. This will significantly speedup future runs. To do so make the following changes to configs/commong/FSConfig.py:

   class RawIdeDisk(IdeDisk):
       image = RawDiskImage(read_only=False)
       def childImage(self, ci):
           self.image.image_file=ci

Then inside of makeArmSystem(), change from:

   self.c0 = CowIdeDisk(driveID='master')

to

   self.c0 = RawIdeDisk(driveID='master')

Be careful when doing this. Any changes made to the disk image will be permanent when using the raw ide disk. To ensure that all the changes are written to the disk image properly you can use the sync and halt Linux commands. These are not available on Android so it is recommended that you use something like Busybox. Once the image has finished booting and settled, you busybox sync and busybox halt -f to write all changes to the disk and halt it properly. You will likely get a panice when the simulator exits regarding an unrecognized byte, this doesn't seem to cause any problems. Remember to re-enable the COW layer once you've finished setting up your disk image.

Busybox

• Busybox is a useful tool providing many common Linux utilities for embedded systems. To build busybox download the source, and compile statically using the following commands:

1. make CROSS_COMPILE=arm-none-linux-gnueabi- defconfig
2. LDFLAGS="--static" make CROSS_COMPILE=arm-none-linux-gnueabi- -jn

Place the busybox binary into the /sbin/ directory of your Android file-system</code>. Run busybox --help to see a full list of the available utilities.

Publications

If you use BBench in your work please cite our IISWC 2011 paper:

A. Gutierrez, R.G. Dreslinski, T.F. Wenisch, T. Mudge, A. Saidi, C. Emmons, and N. Paver. Full-System Analysis and Characterization of Interactive Smartphone Applications. IEEE International Symposium on Workload Characterization, pages 81-90, Austin, TX, November 2011.