@mpx, that's an interesting idea. I think first we're going to try to see if we can just make the GC scale down better. My hypothesis is that the smaller minimum heap size is primarily a problem because of the high constant overheads of starting a GC (it used to be the "small heap amortization problem"—we didn't account properly for all sources of GC work and non-heap work could dominate for small heaps—but the new pacer fixes that). There's probably always going to be some amount of cost for things that genuinely run on very small heaps (after all, a smaller minimum heap trades CPU for RAM in that regime), but my instinct is that it shouldn't be nearly as high as what we're seeing. If we can fix it that way, it may simply obviate the issue.