The performance for the 64–bit Web Server is not necessarily better than the performance for the 32–bit Web Server, but the 64–bit server scales better. Because the 32–bit Web Server process is confined to 4 GB of address space, it can run out of address space when attempting to support simultaneous sessions beyond a certain limit. Even if the host machine has available memory and CPU resources, the 32–bit Web Server might not be able to take advantage of it because of the address space limit. The 64–bit Web Server can run more applications and servlets than the 32-bit server. Also, the 64–bit Web Server can cache several GBs of static content, while the 32-bit Web Server is confined to 4 GB of address space.
In general, the tuning for the 64–bit Web Server is similar to the tuning for the 32–bit Web Server. The differences are mostly tuned at the operating system level. Tuning specifics are discussed in Tuning UltraSPARC® T1–Based Systems for Performance Benchmarking.