- Do you ever find that the Garbage Collector causes noticeable pausing in the emulator?
- Did you do this with 100% managed memory, or do you need to use unsafe code / real pointers?
(Apologies that I didn't read the source code.)
- Do you ever find that the Garbage Collector causes noticeable pausing in the emulator?
The GC dosn't cause noticeable pausing on my setup. Even tho it could allocate less.
- Did you do this with 100% managed memory, or do you need to use unsafe code / real pointers?
In fact it was done without unsafe code or pointers till some of the latest commits. Where i switched to unsafe because performance reasons. On my setup that was arround 10 fps more.
Another thing you can do in C# is leverage stack allocation using structs.
Otherwise, everything looks statically allocated. So there should be no GC collections at all.
There's also managed ways to do that, but they are slower and involve copying memory.
I didn't learn by following someone's example, in my case, I have to work with so many different structs in a high performance use case that I took the time to re-learn pointers. (Haven't used them in years.)
1: Memory is allocated using new byte[bufferSize]
2: That byte[] is pinned to a byte* or void* via fixed
3: The pointer is passed to DeviceIOControl
4: Traditional c-style typecasting inside of fixed
5: Traditional GC cleans up your byte[]. This avoids problems with managed programs that allocate lots of native memory.
I don't know how to use pointers with Span<T>...
BUT: I do similar things with ArraySegment<byte[]>. All that's needed is pointer arithmetic:
ArraySegment<byte> arraySegment = ...
fixed (byte* dataArrayPtr = arraySegment.Array)
{
var dataPtr = dataArrayPtr + arraySegment.Offset;
var ptr = (SomeStruct*)dataPtr;
}I only mention it because I'm not entirely clear on what is going on or how it works (largely because I tend to only be able to learn things by doing them, which is my own issue, not your failure to describe it), but after reading the docs on MemoryMappedFiles, I wonder if it's something that could be useful to you.
However, for an ancient platform on modern hardware I guess the per-frame budget is plentiful even for an emulator.
D also has something similar as compiler switch.
That being said, it is still doable to avoid allocations and the standard library has become much better with not allocating unless really necessary. A lot of the newer things with Span<T> enable zero-allocation usage of certain APIs that before would have allocated.
This requires some care though, as the struct may still be copied needlessly if it is not also marked as `readonly` [2].
[1] - https://blogs.msdn.microsoft.com/mazhou/2018/03/02/c-7-serie... [2] - https://docs.microsoft.com/en-us/dotnet/csharp/write-safe-ef...
The .Net garbage collector is a highly optimized generational garbage collector. Practices like pre-allocating and pooling are discouraged, because most of the time they are premature optimization.
In general, the best way to think about it is to pretend that the garbage collector is a built-in library for pooling and reusing objects.
If, early in your project's lifecycle, you suspect that you'll need to implement your own object pool, just start with stub "Get/Recycle" methods that call new / no-op. You can always swap in a pool later.