From owner-freebsd-stable Wed Apr 24 16:39:41 2002 Delivered-To: freebsd-stable@freebsd.org Received: from falcon.prod.itd.earthlink.net (falcon.mail.pas.earthlink.net [207.217.120.74]) by hub.freebsd.org (Postfix) with ESMTP id A16A337B41E; Wed, 24 Apr 2002 16:39:31 -0700 (PDT) Received: from pool0275.cvx22-bradley.dialup.earthlink.net ([209.179.199.20] helo=mindspring.com) by falcon.prod.itd.earthlink.net with esmtp (Exim 3.33 #2) id 170WLM-000119-00; Wed, 24 Apr 2002 16:38:36 -0700 Message-ID: <3CC741E0.2BB79E0C@mindspring.com> Date: Wed, 24 Apr 2002 16:38:08 -0700 From: Terry Lambert X-Mailer: Mozilla 4.7 [en]C-CCK-MCD {Sony} (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Steve O'Hara-Smith Cc: scrappy@hub.org, freebsd-current@freebsd.org, freebsd-stable@freebsd.org Subject: Re: FreeBSD 4.5-STABLE not easily scalable to large servers ... ? References: <20020422091602.O1721-100000@mail1.hub.org> <3CC40A62.B40E816F@mindspring.com> <20020424191849.3a81b126.steve@sohara.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Steve O'Hara-Smith wrote: > On Mon, 22 Apr 2002 06:04:34 -0700 > Terry Lambert wrote: > > TL> FreeBSD doesn't currently support bank selection. Peter was > TL> working on it, last time I heard. Linux supports it, at an > TL> incredible performance penalty. > > This inspired an off the wall thought that may be insane. Would > it be possible (on a >4Gb system) to address 4Gb of RAM and write a driver > to make the rest appear as a device, which could then be used for a > preferred or (even neater) first level swap. Only if you reserved a window for it. Say 1G of KVA, though last I checked the bank selection granularity wasn't fine enough for that. Memory in the window can *never* be a target for DMA, and should *probably* never be used for kernel structures. If you ever programmed graphics on a TI 99/4A, which has a 4k visible window onto screen memory, or programmed code on the Commodore C64 to use the 32K of RAM-under-ROM, or programmed in DOS or CP/M using Overlays, then you'll be familiar with the problem. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message