documentation on sysctl vm.defer_swapspace_pageouts?

[Geert Hendrickx]

Hi, 

where can I find documentation on the vm.defer_swapspace_pageouts
sysctl?  LINT only mentions it, without explaining, man sysctl doesn't 
mention it at all, and even Google yields very few useful results...  

I was looking for a way to tune swap-usage a bit, I heard Linux has a
"swappiness" setting (telling the kernel how easy it should go with 
paging out), and I hoped FreeBSD would have something similar.
vm.defer_swapspace_pageouts might do the trick, but so it seems to be 
poorly documented...  

GH