Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759557Ab0FJTPA (ORCPT ); Thu, 10 Jun 2010 15:15:00 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:59036 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752472Ab0FJTO6 convert rfc822-to-8bit (ORCPT ); Thu, 10 Jun 2010 15:14:58 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=ct6d9/G5bV1GDQjRLtc4TfbVFeze1eW2tOYC/+UsdxoSIYyqcYctV5qleadcT1ZHS9 8GDVQvdyKhYuBQUQ9OnNgIZklWHh3NxbwF8coidcXJgZuEIsl1dEMXlSke0+CeBh/Rc0 2aiuaTwztYeQZH6w4LIPVLHiE4/gS20Yk5rM0= MIME-Version: 1.0 In-Reply-To: <4C11330A.4040309@nortel.com> References: <877hm64ui4.fsf@basil.nowhere.org> <4C11330A.4040309@nortel.com> Date: Thu, 10 Jun 2010 13:14:57 -0600 Message-ID: Subject: Re: Aerospace and linux From: Brian Gordon To: Chris Friesen Cc: Andi Kleen , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2183 Lines: 51 Thank you both. This has been very helpful for me. I think I read two conclusions: 1) R/O is a small percentage of RAM 2) To cover this small precentage would be non-trivial Thank you both very much for your time and knowledge, I'll move along now. On Thu, Jun 10, 2010 at 12:46 PM, Chris Friesen wrote: > On 06/10/2010 12:38 PM, Brian Gordon wrote: > >> On the more exotic end, I have also seen systems that have dual >> redundant processors / memories. ?Then they add compare logic between >> the redundant processors that compare most pins each clock cycle. ? If >> any pins are not identical at a clock cycle, then something has gone >> wrong (SEU, hardware failure, etc..) > > Some phone switches do this. ?Some of them also have at least two copies > of everything in memory and will do transactional operations that can be > rolled back if there is a hardware glitch. > >> So, some pages of RAM are going to be read-only and the data in those >> pages came from some source (file system?). ? Can anyone describe a >> high level strategy to occasionaly provide some coverage of this data? > >> So far I have thought about page descriptors adding an MD5 hash >> whenever they are read-only and first being "loaded/mapped?" and then >> a background daemon could occasionaly verify. > > Makes sense to me. ?You might also pick an on-disk format with extra > checksumming so you could compare the on-disk checksum with the > in-memory checksum. > > Chris > > -- > The author works for GENBAND Corporation (GENBAND) who is solely > responsible for this email and its contents. All enquiries regarding > this email should be addressed to GENBAND. Nortel has provided the use > of the nortel.com domain to GENBAND in connection with this email solely > for the purpose of connectivity and Nortel Networks Inc. has no > liability for the email or its contents. GENBAND's web site is > http://www.genband.com > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/