Sun Performance and Tuning: Java™ and the Internet, Second Edition

Free Memory—The Memory-Go-Round

Pages of physical memory circulate through the system via “free memory”; the concept seems to confuse a lot of people. This section explains the basic memory flows and describes the latest changes in the algorithm. The section also provides some guidance on when free memory may need tuning and what to change.

First, let’s look at some vmstat output again.

% vmstat 5 procs memory page disk faults cpu r b w swap free re mf pi po fr de sr s0 s1 s5 -- in sy cs us sy id 0 0 0 480528 68056 0 3 5 2 2 0 0 65 12 9 0 165 968 101 2 2 95 0 0 0 476936 85768 0 15 107 0 0 0 0 3 4 7 0 465 1709 231 6 3 91 0 0 0 476832 85160 0 31 144 0 0 0 0 7 0 9 0 597 3558 367 8 6 87 0 0 0 476568 83840 0 7 168 0 0 0 0 4 1 6 0 320 796 155 6 1 ...