From owner-freebsd-performance@FreeBSD.ORG Mon May 5 11:08:04 2003 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 38DE837B401 for ; Mon, 5 May 2003 11:08:04 -0700 (PDT) Received: from xy.hartford.edu (xy.hartford.edu [137.49.19.55]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2F00843F93 for ; Mon, 5 May 2003 11:08:02 -0700 (PDT) (envelope-from knr@xy.hartford.edu) Received: from xy.hartford.edu (knr@localhost.hartford.edu [127.0.0.1]) by xy.hartford.edu (8.12.9/8.12.6) with ESMTP id h45I81Jx000394 for ; Mon, 5 May 2003 14:08:01 -0400 (EDT) (envelope-from knr@xy.hartford.edu) From: "Kyle Rollin" To: freebsd-performance@freebsd.org Date: Mon, 5 May 2003 13:08:01 -0500 Message-Id: <20030505180224.M13866@xy.hartford.edu> In-Reply-To: <3801.172.182.185.39.1052141430.squirrel@bluhayz.homeunix.org> References: <3801.172.182.185.39.1052141430.squirrel@bluhayz.homeunix.org> X-Mailer: Open WebMail 2.00 20030416 X-OriginatingIP: 137.49.19.54 (knr) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Subject: Re: Real and availible RAM X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 05 May 2003 18:08:04 -0000 On Mon, 5 May 2003 09:30:30 -0400 (EDT), agent dero wrote > I have been looking through the kernel boot messages in /var/log > while working on some custom kernel compile work, and I came across something > that I think is very interesting, but doesn't make sense. > real memory = 100663296 (98304K bytes) > avail memory = 94580736 (92364K bytes) > > This tells me that FreeBSD recognizes my 98MB of RAM, but it only > uses 92MB? Are the 6MB of RAM that are left getting shafted, and > just using power, but not being addressed by FreeBSD? Does this slow > down my machine at all, I mean, is there a percentage to this? Where > only x% of 100% RAM is availible or usable? > If you look at the way x86 architecture is designed (and somebody else can feel free to correct me if I'm wrong), but system memory is often used in the caching/shadowing of BIOS. This is where a lot of system memory often goes before the OS is loaded - also, as Rob said, the kernel itself will take up memory before the rest of the OS is booted. If you're concerned that you might run out of memory, RAM is cheap - adding a stick of 128MB will greatly reduce that risk :) -Kyle Rollin