libsmctrl: Quick & Easy Hardware Compute Partitioning on NVIDIA GPUs

This library was developed as part of the following paper:

J. Bakita and J. H. Anderson, "Hardware Compute Partitioning on NVIDIA GPUs", Proceedings of the 29th IEEE Real-Time and Embedded Technology and Applications Symposium, pp. 54-66, May 2023.

Please cite this paper in any work which leverages our library. Here's the BibTeX entry:

@inproceedings{bakita2023hardware,
  title={Hardware Compute Partitioning on {NVIDIA} {GPUs}},
  author={Bakita, Joshua and Anderson, James H},
  booktitle={Proceedings of the 29th IEEE Real-Time and Embedded Technology and Applications Symposium},
  year={2023},
  month={May},
  pages={54--66},
  _series={RTAS}
}

Please see the paper and libsmctrl.h for details and examples of how to use this library. We strongly encourage consulting those resources first; the below comments serve merely as an appendum.

Run-time Dependencies

libcuda.so, which is automatically installed by the NVIDIA GPU driver.

Building

To build, ensure that you have gcc installed and access to the CUDA SDK including nvcc. Then run:

make libsmctrl.a

If you see an error that the command nvcc was not found, nvcc is not available on your PATH. Correct this error by explictly specifying the location of nvcc to make, e.g.:

make NVCC=/playpen/jbakita/CUDA/cuda-archive/cuda-10.2/bin/nvcc libsmctrl.a

For binary backwards-compatibility to old versions of the NVIDIA GPU driver, we recommend building with an old version of the CUDA SDK. For example, by building against CUDA 10.2, the binary will be compatible with any version of the NVIDIA GPU driver newer than 440.36 (Nov 2019), but by building against CUDA 8.0, the binary will be compatible with any version of the NVIDIA GPU driver newer that 375.26 (Dec 2016).

Older versions of nvcc may require you to use an older version of g++. This can be explictly specified via the CXX variable, e.g.:

make NVCC=/playpen/jbakita/CUDA/cuda-archive/cuda-8.0/bin/nvcc CXX=g++-5 libsmctrl.a

libsmctrl supports being built as a shared library. This will require you to distribute libsmctrl.so with your compiled program. If you do not know what a shared library is, or why you would need to specify the path to libsmctrl.so in LD_LIBRARY_PATH, do not do this. To build as a shared library, replace libsmctrl.a with libsmctrl.so in the above commands.

Linking in Your Application

If you have cloned and built libsmctrl in the folder /playpen/libsmctrl (replace this with the location you use):

1. Add -I/playpen/libsmctrl to your compiler command (this allows #include <libsmctrl.h> in your C/C++ files).
2. Add -lsmctrl to your linker command (this allows the linker to resolve the libsmctrl functions you use to the implementations in libsmctrl.a or libsmctrl.so).
3. Add -L/playpen/libsmctrl to your linker command (this allows the linker to find libsmctrl.a or libsmctrl.so).
4. (If not already included) add -lcuda to your linker command (this links against the CUDA driver library).

Note that if you have compiled both libsmctrl.a (the static library) and libsmctrl.so (the shared library), most compilers will prefer the shared library. To statically link against libsmctrl.a, delete libsmctrl.so.

For example, if you have a CUDA program written in benchmark.cu and have built libsmctrl, you can compile and link against libsmctrl via the following command:

nvcc benchmark.cu -o benchmark -I/playpen/libsmctl -lsmctrl -lcuda -L/playpen/libsmctrl

The resultant benchmark binary should be portable to any system with an equivalent or newer version of the NVIDIA GPU driver installed.

Run Tests

To test partitioning:

make tests
./libsmctrl_test_global_mask
./libsmctrl_test_stream_mask
./libsmctrl_test_next_mask

To test that high-granularity masks override low-granularity ones:

make tests
./libsmctrl_test_stream_mask_override
./libsmctrl_test_next_mask_override

And if nvdebug has been installed:

make tests
./libsmctrl_test_gpc_info

Supported GPUs

Known Working

• NVIDIA GPUs from compute capability 3.5 through 8.9, including embedded "Jetson" GPUs
• CUDA 8.1 through 12.2
• x86_64 and Jetson aarch64 platforms

Known Issues

• next_mask will not override stream_mask on CUDA 11.0+
  • As of Feb 2024, a fix for this is coming soon...
• global_mask and next_mask cannot disable TPCs with IDs above 128
  • Only relevant on GPUs with over 128 TPCs, such as the RTX 6000 Ada
• Untested on H100 (compute capability 9.0)
• Untested on non-Jetson aarch64 platforms

Important Limitations

1. Only supports partitioning within a single GPU context. At time of writing, it is challenging to impossible to share a GPU context across multiple CPU address spaces. The implication is that your applications must first be combined together into a single CPU process.
2. No aspect of this system prevents implicit synchronization on the GPU. See prior work, particularly that of Amert et al. (perhaps the CUPiD^RT paper), for ways to avoid this.

Porting to New Architectures

Build the tests with make tests. And then run the following:

for (( i=0; $?!=0; i+=8 )); do MASK_OFF=$i ./libsmctrl_test_stream_mask; done

How this works:

1. If MASK_OFF is set, libsmctrl applies this as a byte offset to a base address for the location of the SM mask fields in CUDA's stream data structure.
2. That base address is the one for CUDA 12.2 at time of writing
3. The stream masking test is run.
4. If the test succeeded (returned zero) the loop aborts, otherwise it increments the offset to attempt and repeats.

Once this loop aborts, take the found offset and add it into the switch statement for the appropriate CUDA version and CPU architecture.