> Its bizarre. the apparent symptoms are: slowness re-painting X11 (eg screen
> refresh from a virtual desktop re-position for mozilla, which is widget rich and
> requires lots of discrete X callbacks to repaint) and a lot more disk noise than

The effect of the new buffer cache code on the vnode cache has already been
noted. I would expect the drag you're experiencing to be largely eliminated
if you'd revert the maximum memory use for the buffer to historic levels,
i.e. to around 5% of physical memory.  To verify that this is the case,
could you do

	`sysctl -w vm.bufcache=5'

and see if that makes the symptoms go away?

-pk