The previous implementation included inactive/cached pages and used
"Pages stored in compressor" (uncompressed size), resulting in inflated
percentages (~88%) that didn't reflect actual memory pressure.
Now uses:
- Anonymous pages (matches Activity Monitor's "App Memory")
- Pages wired down (system memory)
- Pages occupied by compressor (actual RAM used, not uncompressed size)
Also switches to awk for arithmetic to avoid bash integer overflow on
systems with >4GB RAM.
John Ogle
04e1a8563c