Segmented stacks are better even if you have a relocatable stack. GHC switched from monolithic copy-the-whole-thing-to-grow-it to segmented stacks a while ago, and it was a big win. Not just because we waste less space, but because the GC knows when individual stack segments are dirty so that it doesn't need to traverse the whole stack. To avoid the thrashing issue we copy the top 1KB of the previous stack chunk into the new stack chunk when we allocate a new chunk.
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