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I suppose the thing to do is analyse your app for the average string length, and just recompile your Ruby with that. Would be even better of it was a command line parameter.

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This isn't quite right. Even if your average string length is 1k+, you shouldn't change the embedded string size to 1k+. I think these objects sit on the C stack internally, which doesn't handle large objects like this well.

Also, I would guess the performance gains (from skipping malloc) would wash out the longer your average string gets -- even if the huge stack use doesn't kill your performance for some other reason (blowing the d-cache?).

I don't think these strings ever sit on the C stack, except maybe if some C code/extension is being really clever. The standard representation for variables is a tagged pointer as far as I know, so I would assume that is all that goes on the stack. This optimization probably just saves another level of indirection.

Hm, ok. Still, at some level fragmentation is eating gobs of space even if correct for the "average".

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