Re: Best OS & Configuration for Dual Xeon w/4GB & Adaptec

From: Alex Hayward <xelah-pgsql(at)xelah(dot)com>
To: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
Cc: Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, Vivek Khera <vivek(at)khera(dot)org>, Postgresql Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Best OS & Configuration for Dual Xeon w/4GB & Adaptec
Date: 2006-03-21 12:22:31
Message-ID: Pine.LNX.4.58.0603211217420.27598@sphinx.mythic-beasts.com
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On Tue, 21 Mar 2006, Jim C. Nasby wrote:

> On Tue, Mar 21, 2006 at 11:03:26PM +1200, Mark Kirkwood wrote:
> >
> > So its really all about accounting, in a sense - whether pages end up in
> > the 'Buf' or 'Inactive' queue, they are still cached!
>
> So what's the difference between Buf and Active then? Just that active
> means it's a code page, or that it's been directly mapped into a
> processes memory (perhaps via mmap)?

I don't think that Buf and Active are mutually exclusive. Try adding up
Active, Inactive, Cache, Wired, Buf and Free - it'll come to more than
your physical memory.

Active gives an amount of physical memory. Buf gives an amount of
kernel-space virtual memory which provide the kernel with a window on to
pages in the other categories. In fact, I don't think that 'Buf' really
belongs in the list as it doesn't represent a 'type' of page at all.

--
Alex Hayward
Seatbooker

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