On Thu, 30 Nov 2006, Peter Zijlstra wrote:

Right, perhaps my bad in wording the intent; the needed information is
how many more pages would I need to grow the slab with in order to store
so many new object.

Would you not have to take objects currently available in 
caches into account? If you are short on memory then a flushing of all the 
caches may give you the memory you need (especially on a system with a 
large number of processors).