> currently, since amaps are not extended *backwards*, there's no way to
> merge a new entry forwards with an existing entry *if* the following
> entry is backed by an amap.  a bimerge is simply a new allocation that
> filled the gap between two existing allocations.  plain forward merges
> actually occur rather infrequently.

Suppose following case:

prev_entry wi/ amap | gap will be filled by new entry | next_entry w/o amap 

	   A			  B				   C

The resulting entry covers A+B+C but amap only covers A+B, doesn't it?

enami.