From owner-freebsd-questions@FreeBSD.ORG Sun Sep 4 05:12:55 2011 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 97BC2106566C for ; Sun, 4 Sep 2011 05:12:55 +0000 (UTC) (envelope-from brett@lariat.net) Received: from lariat.net (lariat.net [66.119.58.2]) by mx1.freebsd.org (Postfix) with ESMTP id 1B3B98FC20 for ; Sun, 4 Sep 2011 05:12:54 +0000 (UTC) Received: from WildRover.lariat.net (IDENT:ppp1000.lariat.net@lariat.net [66.119.58.2]) by lariat.net (8.9.3/8.9.3) with ESMTP id XAA29689 for ; Sat, 3 Sep 2011 23:12:50 -0600 (MDT) Message-Id: <201109040512.XAA29689@lariat.net> X-Mailer: QUALCOMM Windows Eudora Version 7.1.0.9 Date: Sat, 03 Sep 2011 23:12:52 -0600 To: questions@freebsd.org From: Brett Glass Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Cc: Subject: Re: Huge interrupt overhead reported after RAM added to Atom-based system 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: Sun, 04 Sep 2011 05:12:55 -0000 Have been doing more experimentation regarding this problem. It doesn't occur with a 1 GB memory module in the machine, nor with a 2 GB module -- only a 4 GB module. This makes me wonder if there's some sort of memory bank switching or extended addressing mechanism here (like PAE). Perhaps it's causing some sort of interrupt every time a certain area of memory (perhaps the topmost portion) is accessed? I'd like to experiment with having FreeBSD try to use less than the full 4 GB (e.g., to make it act as if memory ended at, say, 3 GB) but I'm not sure how to tell the kernel to do that. --Brett Glass