Begin pontification!

There are a few golden rules in high performance server development:

• use the right algorithm / data structure for the job
• precompute as much as you can
• avoid system calls

Usually this boils down to an offline (or high latency) system that sends data to a fast serving tier via message replication or file push.

And basically the only way to read data from a file without syscalls is with mmap.

Too bad Java’s mmap implementation was so half-assed. In Java 1.5 (and possibly 1.6, I’m not sure), you…

• can’t map files larger than 2 GB (yay signed integers!)
• can’t do a bulk copy from an absolute position
• can’t even unmap an mapped file!

The rationale for the non-resolution or won’t-fix status of these bugs is pretty sad/hilarious, or as I prefer, “sadlarious”.

It’s basically “we designed NIO in 1973″ and “obscure security issue means we’ll reclaim that memory when we feel like it”.