CUDA Flux: A Lightweight Instruction Profiler for CUDA Applications

CUDA Flux is a profiler for GPU applications which reports the basic block executions frequencies of compute kernels

Dependencies

• LLVM:
  CUDA Flux is tested and developed with llvm 11.0

  git clone --branch release/11.x https://github.com/llvm/llvm-project.git
  

  CMake config:

  cmake -DLLVM_ENABLE_PROJECTS=clang -DCMAKE_INSTALL_PREFIX=/opt/llvm-11.0 \
  -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=ON \
  -DLLVM_ENABLE_DOXYGEN=OFF -DLLVM_BUILD_DOCS=OFF -GNinja \
  -DLLVM_INSTALL_BINUTILS_SYMLINKS=ON -DBUILD_SHARED_LIBS=ON \
  ../llvm
  

• re2c lexer generator - http://re2c.org/ (make sure to check your package manager first)

• CUDA SDK >= 9.0

• Python (python3 preferred) with the yaml package installed

• environment-modules (optional, but recommended)

Install

# Make sure LLVM and CUDA are in your paths
git clone https://github.com/UniHD-CEG/cuda-flux.git
cd cuda-flux && mkdir build && cd build
cmake -DCMAKE_INSTALL_PREFIX=/opt/cuda-flux .. # change install dir if you wish
make install

Usage

Make sure the bin folder of your cuda-flux installation is in your path. Better: use environment-module to load cuda-flux.

module load /opt/cuda-flux/module/cuda_flux # LLVM and CUDA need to be loaded first!

Compile your CUDA application:

clang_cf++ --cuda-gpu-arch=sm_35 -std=c++11 -lcudart test/saxpy.cu -o saxpy`

Execute the binary like usual: ./saxpy

Output:
If any kernel was executed there is a bbc.txt file. Each kernel execution results in a line with the following information:

• kernel name
• gridDim{X,Y,Z}
• blockDim{X,Y,Z}
• shared Memory size
• Profiling Mode (full, CTA, warp)
• List of executions counters for each block

The PTX instructions for all kernels are stored in the PTX_Analysis.yml file. The order of the Basic Blocks corresponds with the order of the counters in the bbc.txt file.

Profiling mode is controlled by the environment variable MEKONG_PROFILINGMODE. If is is not set or set to 0 all threads are profiled, which is the recommended setting. export MEKONG_PROFILINGMODE=1 will only profile one CTA and export MEKONG_PROFILINGMODE=2 will profile only one warp.