alt Hacker NewsThe thing is it's easy to define free, unused memory. But a lot of the used memory is your system caching stuff that would be free if you needed more than what's actually free. So you can see you have 1g of free memory out of your 4g, but then you allocate 3g and it will do without a sweat and you'd be confused. So you have to go and dig for what those caches are and report that they're effectively free too.
Instantly reclaimable disk caches should count as available, and they do.
This isn’t hard. The OS should just expose a counter for available memory instead of having applications understand every type of memory reservation.
edit:
Linux does this, but it has its own share of issues with memory counters. The “cached” memory includes tmpfs and ramfs for seemingly no reason.