Is something wrong with the generational collector? It can be tweaked
pretty finely; read the Hotspot VM command option documentation.

If need be, I think current Sun VMs can be given options that make
them use alternative collectors, probably including a nongenerational
one.

Most likely, you really just need the right command line option to
Sun's VM, rather than a different VM implementation altogether, to
achieve whatever it is you are looking for here.