C++ – GDI versus Direct2D

I'm programming a simulation at the moment, and I want to port my application from using GDI to using Direct2D. But my Direct2D code is much slower than my GDI code.

I render a lot of ellipses on the screen. In my GDI application I draw to a memory device context and then use BitBlt to draw on the windows device context. With Direct2D, I draw onto a ID2D1HwndRenderTarget.

My Problem is, when using GDI, I can draw easily 400+ ellipses and still have 400 FPS. When I do the same number of ellipses with Direct2D, my FPS drops down to 30FPS.

I already switched antialiasing off but it doesn't really help. The interesting thing is that drawing just a few ellipses is faster in Direct2D compared to GDI. Is there anything I can do to improve the performance in Direct2D, or should I keep my application using GDI?

Here is my drawing code using GDI:

VOID Begin() {
    SelectObject(this->MemDeviceContext, this->MemoryBitmap);
    this->BackgroundBrush = CreateSolidBrush(this->BackgroundColor);
    HBRUSH OldBrush = (HBRUSH)SelectObject(this->MemDeviceContext, this->BackgroundBrush);
    Rectangle(this->MemDeviceContext, -1, -1, 801, 601);
    SelectObject(this->MemDeviceContext, OldBrush);
    DeleteObject(this->BackgroundBrush);
    SetViewportOrgEx(this->MemDeviceContext, 400, 300, &this->OldOrigin);
}
VOID End() {
    SetViewportOrgEx(this->MemDeviceContext, this->OldOrigin.x, this->OldOrigin.y, 0);
    BitBlt(this->DeviceContext, 0, 0, 800, 600, this->MemDeviceContext, 0, 0, SRCCOPY);
}

Between my Begin and End function, I draw my ellipses the standard GDI way.

Here are my begin and end functions using Direct2D:

VOID BeginDrawing() {
    this->RenderTarget->BeginDraw();
    RenderTarget->Clear(D2D1::ColorF(D2D1::ColorF::CornflowerBlue));
    RenderTarget->SetTransform(this->ScalingMatrix * this->TranslateMatrix);
}
VOID EndDrawing() {
    this->RenderTarget->EndDraw();
}

And here is how I set up my Direct2D interfaces. It's all wrapped in class; that's why I cant post the full code:

    if(D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &Direct2DFactory) != S_OK)
        throw std::runtime_error("RENDERWINDOW::InitializeDirect2D: Failed to create a factory interface.");
    RECT WindowRect;
    memset(&WindowRect, 0, sizeof(RECT));
    GetClientRect(this->WndHandle, &WindowRect);
    D2D1_SIZE_U WindowSize = D2D1::SizeU(WindowRect.right, WindowRect.bottom);
    Direct2DFactory->CreateHwndRenderTarget(D2D1::RenderTargetProperties(D2D1_RENDER_TARGET_TYPE_HARDWARE), 
    D2D1::HwndRenderTargetProperties(this->WndHandle, WindowSize, D2D1_PRESENT_OPTIONS_IMMEDIATELY), &RenderTarget);

Thank you in advance.