Vboxsf has no read caching on linux

[Slava Nadvorny]

There is no read caching implemented on volumes mounted via vboxsf on linux guest. Read cache may improve vboxfs performance dramatically.

For testing try executing

time cat any_long_file > /dev/null

on mounted host fs multiple times. Time to read file does not change. That means there is no caching done on that file. Dong the same i.e. on vmware fusion shares makes subsequent reading almost instant.