From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 6 May 2002 05:49:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 6 May 2002 05:49:27 -0400 Received: from [195.39.17.254] ([195.39.17.254]:22420 "EHLO Elf.ucw.cz") by vger.kernel.org with ESMTP id ; Mon, 6 May 2002 05:49:23 -0400 Date: Sat, 27 Apr 2002 01:15:34 +0000 From: Pavel Machek To: "Richard B. Johnson" Cc: Tony Luck , linux-kernel@vger.kernel.org Subject: Re: Virtual address space exhaustion (was Discontigmem virt_to_page() ) Message-ID: <20020427011534.C413@toy.ucw.cz> In-Reply-To: <20020503183701.32163.qmail@web13505.mail.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > One of the Unix characteristics is that the kernel > > > address space is shared with each of the process > > > address space. > > > > This hasn't been an absolute requirement. There have > > been 32-bit Unix implementations that gave separate > > 4G address spaces to the kernel and to each user > > process. The only real downside to this is that > > copyin()/copyout() are more complex. Some processors > > provided special instructions to access user-mode > > addresses from kernel to mitigate this complexity. > > > Really? The only 32-bit Unix's I've seen the details of > are SCO Unix, Interactive Unix, Linux, and BSD Unix. > The other Unix's I've become familiar are Sun-OS, the > original AT&T(Unix System Labs)/SYS-V and DEC Ultrix. > All these Unix's share user address-space with kernel > address-space. This is supposed to be the very thing Remember userspace being accessed through fs: in linux-2.0 days? That counts as separate address space to me... Pavel -- Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt, details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.