> When you have 512MiB of memory and your current allocation is 256MiB, where do you go?

Then you're out of luck no matter what strategy you use. Even allocating 256MiB + 1 byte won't work, because you can't deallocate the old buffer until the new one has been allocated.

> Also when your dataset allocates 64MiB up front, then chucks two bytes on the end, where do you go?

What I didn't say in the article is that for some of the Firefox examples where the buffers can get really large -- such as nsTArray -- it switches to a growth rate of 1.125 once it gets to 8 MiB. So in that case it would grow to 72 MiB.