Keeping Information Near the CPU

Moving information between various storage areas happens automatically. Compilers determine which information should be stored in registers. CPU chip logic keeps recently used information in the CPU cache. The operating system controls which information is stored in RAM and shuttles it back and forth from the disk drive.

CPU registers and the CPU cache cannot be effectively tuned by the database administrator. Effective database tuning involves increasing the amount of useful information in RAM, thus preventing disk access where possible.

You might think this is easy to do, but it is not. A computer's RAM contains many things:

• executing programs
• program data and stack
• POSTGRESQL shared buffer cache
• kernel disk buffer cache
• kernel

Proper tuning involves keeping as much database information in RAM as possible while not adversely affecting other areas of the operating system.