From owner-freebsd-questions@FreeBSD.ORG Fri Oct 3 12:43:08 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 13EC11065693 for ; Fri, 3 Oct 2008 12:43:08 +0000 (UTC) (envelope-from fbsd06+2L=adfcea19@mlists.homeunix.com) Received: from fallback-in1.mxes.net (fallback-out1.mxes.net [216.86.168.190]) by mx1.freebsd.org (Postfix) with ESMTP id D9B7C8FC1D for ; Fri, 3 Oct 2008 12:43:07 +0000 (UTC) (envelope-from fbsd06+2L=adfcea19@mlists.homeunix.com) Received: from mxout-03.mxes.net (mxout-03.mxes.net [216.86.168.178]) by fallback-in1.mxes.net (Postfix) with ESMTP id 654251646AF for ; Fri, 3 Oct 2008 08:26:27 -0400 (EDT) Received: from gumby.homeunix.com. (unknown [87.81.140.128]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTP id 86E1B23E49B for ; Fri, 3 Oct 2008 08:26:23 -0400 (EDT) Date: Fri, 3 Oct 2008 13:26:17 +0100 From: RW To: freebsd-questions@freebsd.org Message-ID: <20081003132617.4c53001c@gumby.homeunix.com.> In-Reply-To: <200810020958.54563.kirk@strauser.com> References: <200810020958.54563.kirk@strauser.com> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.11; i386-portbld-freebsd7.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: More RAM for buffers? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 03 Oct 2008 12:43:08 -0000 On Thu, 2 Oct 2008 09:58:54 -0500 Kirk Strauser wrote: > I have an AMD system with 6GB of RAM. From dmesg: > > usable memory = 6428237824 (6130 MB) > avail memory = 6203797504 (5916 MB) > > However, most of it is just sitting there when it looks like it could > be used for buffers or cache: > > Mem: 1186M Active, 3902M Inact, 468M Wired, 233M Cache, 214M Buf, > 138M Free Swap: 8192M Total, 900K Used, 8191M Free > > Since I've yet to find a great explanation for what the different > types of memory are, could someone say why all that inactive memory > is better than using it for cache or buffers? The terms are a bit misleading, because the don't all relate to the use of the memory from the user's perspective, but how it's seen within FreeBSD's integrated cache/VM system. Active, Inact, Cache and Free are all part of the life-cycle of normal memory pages, they hold pretty much everything used by processes, and disk-caching. "Cache" actually has little to do with caching as such; it contains pages that are still holding data, but can be reused instantaneously because they are consistent with their backing store. In not exactly sure what "Buf" is, but I guess it's low-level disk buffering memory, that can't be discarded the way normal disk caching pages can.