nginx/freebsd kern.maxbcache

[Richard Kearsley]

Hi

I'm trying to tune 'kern.maxbcache' with hope of increasing 
'vfs.maxbufspace' so that more files can be stored in buffer memory on 
freebsd 9.1
It's suggested to tune this value here 
http://serverfault.com/questions/64356/freebsd-performance-tuning-sysctls-loader-conf-kernel 
and here http://wiki.nginx.org/FreeBSDOptimizations
However, I can't get the value of 'vfs.maxbufspace' to increase:
kern.maxbcache: 21474836480
vfs.maxbufspace: 3441033216

Did anyone else use this tunable and get results?

Many thanks
Richard