From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f180.google.com (mail-ie0-f180.google.com [209.85.223.180]) by kanga.kvack.org (Postfix) with ESMTP id 33F9F6B0035 for ; Thu, 30 Jan 2014 15:26:29 -0500 (EST) Received: by mail-ie0-f180.google.com with SMTP id at1so3625616iec.25 for ; Thu, 30 Jan 2014 12:26:28 -0800 (PST) Received: from merlin.infradead.org (merlin.infradead.org. [2001:4978:20e::2]) by mx.google.com with ESMTPS id jc1si36922112igb.69.2014.01.30.12.26.24 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Jan 2014 12:26:25 -0800 (PST) Message-ID: <52EAB56E.2030102@infradead.org> Date: Thu, 30 Jan 2014 12:26:22 -0800 From: Randy Dunlap MIME-Version: 1.0 Subject: Re: [BUG] Description for memmap in kernel-parameters.txt is wrong References: <52EAA714.3080809@infradead.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andiry Xu Cc: linux-kernel@vger.kernel.org, Andiry Xu , Linux MM On 01/30/2014 11:33 AM, Andiry Xu wrote: > On Thu, Jan 30, 2014 at 11:25 AM, Randy Dunlap wrote: >> [adding linux-mm mailing list] >> >> On 01/30/2014 08:52 AM, Andiry Xu wrote: >>> Hi, >>> >>> In kernel-parameters.txt, there is following description: >>> >>> memmap=nn[KMG]$ss[KMG] >>> [KNL,ACPI] Mark specific memory as reserved. >>> Region of memory to be used, from ss to ss+nn. >> >> Should be: >> Region of memory to be reserved, from ss to ss+nn. >> >> but that doesn't help with the problem that you describe, does it? >> > > Actually it should be: > Region of memory to be reserved, from nn to nn+ss. > > That is, exchange nn and ss. Yes, I understand that that's what you are reporting. I just haven't yet worked out how the code manages to exchange those 2 values. >> >>> Unfortunately this is incorrect. The meaning of nn and ss is reversed. >>> For example: >>> >>> Command Expected Result >>> memmap 2G$6G 6G - 8G reserved 2G - 8G reserved >>> memmap 6G$2G 2G - 8G reserved 6G - 8G reserved >> >> Are you testing on x86? >> The code in arch/x86/kernel/e820.c always parses mem_size followed by start address. >> I don't (yet) see where it goes wrong... >> > > Yes, it's a x86 machine. > >> >>> Test kernel version 3.13, but I believe the issue has been there long ago. >>> >>> I'm not sure whether the description or implementation should be >>> fixed, but apparently they do not match. >> >> I prefer to change the documentation and leave the implementation as is. >> > > That's fine. memmap itself works OK, it's just the description is > wrong and people like me get confused. > > Thanks, > Andiry -- ~Randy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org