===== Getting Started =====

gem5-gpu, like gem5, uses [[http://mercurial.selenic.com/|mercurial]] for version control. A short guide to mercurial can be found [[http://mercurial.selenic.com/guide/|here]]. A much longer, exhaustive coverage of mercurial can be found in the hg book, available online [[http://hgbook.red-bean.com/|here]].

Since gem5-gpu builds off of other projects, rather than fork gem5 and GPGPU-Sim, we make heavy use of mercurial patch queues. For more information, see the hg book chapter on patch queues: [[http://hgbook.red-bean.com/read/managing-change-with-mercurial-queues.html|http://hgbook.red-bean.com/read/managing-change-with-mercurial-queues.html]]. 

==== Required Software ====
Since we build off of gem5, all of the dependencies of gem5 are also dependencies of gem5-gpu. It is suggested that before you try to compile gem5-gpu you compile a copy of gem5 to ensure these baseline dependencies are met. gem5 dependencies can be found [[http://gem5.org/Dependencies|here]], and more gem5 information can be found [[http://gem5.org/|here]].

One dependency in addition to the gem5 dependencies is a CUDA installation to have access to nvcc and header files. When you have CUDA installed, export the following environment variable used during gem5-gpu build:
<code>
export CUDAHOME=/path/to/your/cuda/install/cuda
</code>

The versions of software we have used to test gem5-gpu are listed [[http://goo.gl/S1ts6|here]]. Deviations from the tested versions may cause errors.
==== Create directory ====
   * mkdir gem5-gpu
   * cd gem5-gpu

==== Clone gem5 and gem5-patches ====

You’ll need the gem5 revision found [[http://goo.gl/S1ts6|here]]. This revision is the latest that is known to work with gem5-gpu.

<code>
hg qclone http://repo.gem5.org/gem5 -p http://gem5-gpu.cs.wisc.edu/repo/gem5-patches
cd gem5/
hg update -r <gem5-revision>
hg qpush -a
cd ../
</code>
==== Clone GPGPU-Sim and GPGPU-Sim patches (2 separate options) ====

A) The easy way (recommended):
<code>
hg qclone http://gem5-gpu.cs.wisc.edu/repo/gpgpu-sim -p http://gem5-gpu.cs.wisc.edu/repo/gpgpu-sim-patches
cd gpgpu-sim
hg qpush -a
cd ../
</code>

B) To have full control of GPGPU-Sim (harder):

If you would like to test extensions to the PTX ISA, you may need to modify the Lex+Yacc ISA parser in GPGPU-Sim to enable these extensions. In order to do this, you will need to generate your own ISA parser source code within the GPGPU-Sim code base. Below are instructions for setting up gem5-gpu using the full GPGPU-Sim source to allow for these ISA modifications.

You’ll need the “gpgpu-sim-sha” found [[http://goo.gl/S1ts6|here]]. **NOTE:** If you setup GPGPU-Sim from the public git server instead of pulling from our repositories, you may not be able to submit review requests to our GPGPU-Sim patches repository

<code>
git clone git://dev.ece.ubc.ca/gpgpu-sim gpgpu-sim-complete
cd gpgpu-sim-complete
git checkout <gpgpu-sim-sha>
    # This updates GPGPU-Sim the latest version that works with gem5-gpu
cd v3.x
source setup_environment release
make
cd ../../
ln -s gpgpu-sim-complete/v3.x/src gpgpu-sim
cd gpgpu-sim
hg init
cd .hg/
hg clone http://gem5-gpu.cs.wisc.edu/repo/gpgpu-sim-patches patches
cd ../
hg add
hg ci -m “Initializing GPGPU-Sim Mercurial base”
hg qpush -a
cd ../
</code>
==== Clone gem5-gpu glue code ====
<code>
hg clone http://gem5-gpu.cs.wisc.edu/repo/gem5-gpu
</code>

==== Build ====

Below are quick start commands to build and run gem5-gpu with the x86 CPU ISA. For building and running gem5-gpu with the ARM32 CPU ISA, see instructions here: [[arm32_support|ARM32 Support]].

<code>
cd gem5
scons build/X86_VI_hammer_GPU/gem5.opt --default=X86 EXTRAS=../gem5-gpu/src:../gpgpu-sim/ PROTOCOL=VI_hammer GPGPU_SIM=True
</code>

You can also build using the pre-defined build options files (found in gem5-gpu/build_opts) as follows:

<code>
cd gem5
scons build/X86_VI_hammer_GPU/gem5.opt --default=../../../gem5-gpu/build_opts/X86_VI_hammer_GPU EXTRAS=../gem5-gpu/src:../gpgpu-sim/
</code>

==== Running gem5-gpu ====

gem5-gpu is run the same way as gem5. Here is an example of how to run with syscall emulation mode (requires that you build benchmarks per instructions [[benchmarks|here]]):

<code>
build/X86_VI_hammer_GPU/gem5.opt ../gem5-gpu/configs/se_fusion.py -c /path/to/your/benchmarks/rodinia/backprop/gem5_fusion_backprop -o 16
</code>

The configuration file se_fusion.py constructs a simulated system with CPU and GPU cores, and the benchmark runs on the "bare metal" simulated hardware. To see the full set of options supported by se_fusion.py, run the following:

<code>
build/X86_VI_hammer_GPU/gem5.opt ../gem5-gpu/configs/se_fusion.py --help
</code>

Syscall emulation mode is limited to simulating benchmarks that call a restricted subset of system calls implemented in gem5. However, gem5-gpu also support full-system simulation, which allows for booting an operating system and running multiprocess and multithreaded workloads.

To run gem5-gpu in full-system mode, the following command will boot Linux (assuming you have setup a kernel and disk image per [[http://gem5.org/Running_gem5#Full_System_.28FS.29_Mode|gem5 instructions]]). We may release disk images in the future, so if you are interested, please email the list.

<code>
build/X86_VI_hammer_GPU/gem5.opt ../gem5-gpu/configs/fs_fusion.py
</code>