I spontaneously decided to copy over the entire Gentoo stage3 filesystem to my external hard-disk, which is recognized as a general USB storage device under linux. NFS was taking waaaaay too long for this compilation. I had checked everything out with top, under linux, played with the swappiness parameter in /proc/sys/vm, and also attempted to renice the jikes processes' priority to a whopping 17! Non of those had a major effect on the cpu-usage of the jikes process. The highest that I'd seen it was 10% for a whole 2 seconds.
The problem lies with NFS root and the overhead associate not only with RPC, but also the fact that my swap was also on the NFS root, effectively squaring the complexity of the overhead. With my Gentoo stage 3 root filesystem located on a locally attached usb storage device, along with the swap file, the speed of compilation increased dramatically! The jikes process has just started and its already achieved 50% of the cpu time! That's up from an average of maybe 3% with the tweaking I mentioned previously.
I'd better mention this to Dave as well, so that he's not stuck ever repeating my stupid mistake of compiling on an NFS root!