IL2CXX is yet another .NET IL to C++ transpiler.
This is an EXPERIMENTAL study to see the potential of Recylone.
There are a lot of missing pieces in .NET runtime support as they are implemented as needed.
- .NET 8
- C++20
Currently, it is built and tested only on Linux x86-64.
cd IL2CXX.Tests
LD_LIBRARY_PATH=$DOTNET_ROOT/shared/Microsoft.NETCore.App/8.0.x dotnet test
This requires a lot of memory.
Specify NUnit.NumberOfTestWorkers based on the available memory.
LD_LIBRARY_PATH=$DOTNET_ROOT/shared/Microsoft.NETCore.App/8.0.x dotnet test -- NUnit.NumberOfTestWorkers=2
cd IL2CXX.Console
dotnet run --target Unix --out out-Foo .../Foo.dll
mkdir out-Foo/build
cd out-Foo/build
CXX=clang++ cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=1 ..
cmake --build . -j8 # or whatever
LD_LIBRARY_PATH=$DOTNET_ROOT/shared/Microsoft.NETCore.App/8.0.x ./Foo
cmake --build . takes really long time.
Below are build durations running the above commands on my Core i7-8550U laptop:
- MonoGame.Samples Platformer2D - 5 minutes
- bepuphysics2 Demos.GL - 12 minutes
- Platformer2D - Platformer2D of MonoGame.Samples
- Demos - Demos.GL of bepuphysics2
- WebGLGears - WebGL Gears
- DemosWasm - A WebAssembly Port of Demos.GL of bepuphysics2
I compared GC pauses in IL2CXX to those in .NET 6 preview using the same way introduced by this blog post.
The full code is in gc_latency_experiment directory.
Below is the result:
Regarding latency distribtion, IL2CXX looks better than both the Workstation GC (WKS) and the Server GC (SVR) of .NET 6 preview. Regarding total time, SVR is the fastest. (SVR < IL2CXX < WKS)
IL2CXX is advantageous in this particular case because no cycles (cyclic object graphs) are involved in the case. Without cycles, all it has to do is concurrent reference counting, and running cycle collection only increases GC pause.
Another thing found here is that the max GC pause in IL2CXX is two times longer than that in the Workstation GC. There are several options to consider in order to reduce the max GC pause:
- Size of increment/decrement queues.
recyclone::t_slot<>::t_incrementsrecyclone::t_slot<>::t_decrements
- Frequency of cycle collection.
recyclone::t_engine<>::v_collector__threshold
- Batch size of cycle collection.
Currently, the last item can not be adjusted. The cycle collection always processes all the candidate roots at once. I think it is possible to change the cycle collection to finish early leaving the rest of the candidate roots to the next epoch.
The MIT License (MIT)
Copyright (c) Shin-ichi MORITA
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