When I changed my kernel some months ago to use the 64G flag I tried to find actual data as well.
I understand perfectly that the memory switching will cause some overhead, but personally I have not 'felt' any differences between the two kernels.
I started a search for some reliable benchmarking tools but gave up after a while.
Benchmarking a system is not trivial:
- do you want to test memory access?
- disk I/O?
- network I/O?
It all depends on what you use your server for.
I have seen servers with 20 - 30% processor usage but terrible response times because of long disk I/O queues or network latency problems.
I have seen processors cooking at 100% usage because of badly written database apps.
And I know of dozens of 32-bit servers (Windows & Linux) using PAE and performing very well and other 64-bit servers with lots of memory only causing performance head-aches.
By the way, managing data centers is my job