Well, I was replying to xav who seems to have a test case which is a lot quicker on other Unix systems.
I can imagine that having a database with 2 Gbytes data to manage would need quite a bit of virtual memory even if it is correctly written.
If that application recompiled for the other Unix is definitely quicker, it may be due to the too small granularity of the pages on ia32, forcing the same treatment (for instance write of copy-on-write pages) to be done hundred of thousands of times.
Even if the code is optimised, it will be slow.
The nice thing of 4 Kbytes memory pages is that the filesystem code (which has 4 Kbytes blocks) is simpler (things like paging-in memory mapped files on read).
Would be nice to know if another Unix on ia32 processor is quicker, or simply another processor is quicker on the test case.
But as I said, I am not a specialist of virtual memory.