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Date:      Thu, 21 Nov 2002 15:27:40 -0800
From:      David Schultz <dschultz@uclink.Berkeley.EDU>
To:        Avleen Vig <lists-freebsd@silverwraith.com>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: Buf, Wired and Inact memory
Message-ID:  <20021121232740.GF6062@HAL9000.homeunix.com>
In-Reply-To: <20021120212305.H21698-100000@apple.silverwraith.com>
References:  <20021120212305.H21698-100000@apple.silverwraith.com>

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Thus spake Avleen Vig <lists-freebsd@silverwraith.com>:
> I understand that Inact memory is memory that has been requested by
> processes but not in use. Is this correct?
> 
> I don't understand however, what Buf and Wired memory is used for. How
> many I free some of this up for use by my other processes?

An inactive page is one that a process used at one time, but which
hasn't been used for a while and is a candidate for being swapped
out if memory pressure on the system increases.  A cached page is
has already been written to stable storage and can be immediately
reused if necessary.  However, cached pages can also be reused by
the processes that own them without having to fetch the contents
from disk again.

Wired memory, on the other hand, is memory that can never be paged
out.  Typically kernel memory falls into this category, although
user processes may request that some of their pages be wired as
well.

`Buf', as reported by top(1), refers to the size of the
filesystem buffer cache, which is statically allocated and used
for I/O.

> The top of my Top output looks like:
> 66 processes:  2 running, 64 sleeping
> CPU states:  1.5% user,  0.0% nice,  1.5% system,  0.0% interrupt, 96.9% idle
> Mem: 49M Active, 37M Inact, 27M Wired, 6000K Cache, 22M Buf, 5448K Free
> Swap: 256M Total, 5920K Used, 250M Free, 2% Inuse
> 
> Yeah it's a fairly idle system but has a few stability issues which I
> think as disk related.
> It's running qmail, djbdns (may switch to bind but i know that would use
> more memory), apache 2, and some user apps like pine, irssi, screen, etc.
> 
> Any advice on optimizin memory usage would be really appreciated. It's
> only a little P166 with 128Mb :-)

This looks normal for an unloaded system.  Your system isn't
paging, so what are you worried about?

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