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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Tue, 24 Mar 2015 13:08:10 +1100

> For the large pool, we don't keep a hint so we don't know it's
> wrapped, in fact we purposefully don't use a hint to limit
> fragmentation on it, but then, it should be used rarely enough that
> flushing always is, I suspect, a good option.

I can't think of any use case where the largepool would be hit a lot
at all.