understanding freebsd memory usage

Fri, 30 Jan 2009 22:07:17 +0000

I think it is better to write in english, since I’m often googling around about some problem and land on a site in chinese with some configuration pasted in the site.

The problem is I don’t know what poor chinese boy wrote: “This configuration is working for me:” or “This configuration is not working at all, can someone help me:”. So I try it. Never worked.

Recently I found a post which nicely describes statuses of FreeBSD memory allocation.

Top shows:

Mem: 4589M Active, 13G Inact, 489M Wired, 733M Cache, 214M Buf, 886M Free

And the snip from the post:

Memory normally moves along the following path:

Wired -> Active -> Inactive -> Cached -> Free

and then when it gets allocated and used it moves back to Wired.

The difference between the categories is mainly that “Inactive” and
“Cached” memory still contains data that the system might be able to
reuse, while “Free” memory is completely free and unused.
In order to use Cached or Inactive memory it might need to be flushed
first, with Inactive probably being dirty and Cached probably not.
(“Active” memory is almost certainly dirty and is therefore somewhat
more expensive to reuse.

Memory on Simon Žekar — unix, communications, stupidities

understanding freebsd memory usage