memory usage for 9.2.4

[Chris Stromsoe]

I'm running bind 9.2.4 and am regularly seeing it use > 1.5Gb ram.  I'm loading 
~ 1050 zones and an RBL zone.  The zones on disk are 132680Mb (measured with 
du).  rndc dumpdb produces a 40Mb dump file.

Immediately after startup completes, bind is using slightly less than 500Mb. 
max-cache-size is set to 250M.  The machine has 1Gb of physical memory + 2Gb 
swap.

I would expect memory usage to stabilize somewhere around 750Mb, but it 
doesn't.  After a few weeks of running, the amount of swapping becomes 
noticeable and I have to kill and restart named.  Are there issues with 
max-cache-size in 9.2.4?  Or am I missing something obvious?

-Chris