Background writer memory bloat?

I'm seeing a background writer process in an 8.0.8 installation that uses 1.6
GB of main memory, and ps shows that it has used an unreasonable amount of
CPU time so far.  It seems that the machine was under heavy load just before
I got to it; maybe that is cause?  Has anyone seen this sort of memory bloat
on the background writer process?

--
Peter Eisentraut
http://developer.postgresql.org/~petere/