From: Randy Dunlap <rdunlap@infradead.org>
To: Andiry Xu <andiry@gmail.com>
Cc: linux-kernel@vger.kernel.org, Andiry Xu <andiry.xu@gmail.com>,
Linux MM <linux-mm@kvack.org>
Subject: Re: [BUG] Description for memmap in kernel-parameters.txt is wrong
Date: Thu, 30 Jan 2014 12:26:22 -0800 [thread overview]
Message-ID: <52EAB56E.2030102@infradead.org> (raw)
In-Reply-To: <CAOvWMLbs-sP+gJHV_5O6ZbV8eTpEKPVRVR238gFcPQeqhCjT3A@mail.gmail.com>
On 01/30/2014 11:33 AM, Andiry Xu wrote:
> On Thu, Jan 30, 2014 at 11:25 AM, Randy Dunlap <rdunlap@infradead.org> 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
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next prev parent reply other threads:[~2014-01-30 20:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAOvWMLa334E8CYJLrHy6-0ZXBRneoMf-05v422SQw+dbGRubow@mail.gmail.com>
2014-01-30 19:25 ` [BUG] Description for memmap in kernel-parameters.txt is wrong Randy Dunlap
2014-01-30 19:33 ` Andiry Xu
2014-01-30 20:26 ` Randy Dunlap [this message]
2014-01-30 22:17 ` David Rientjes
2014-01-30 22:54 ` Randy Dunlap
2014-01-30 23:43 ` Andiry Xu
2014-01-30 23:49 ` Randy Dunlap
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