linux-kernel - Re: Memory not being reported

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Date:	Sun, 25 Jan 2009 14:10:38 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	ronis@...ispc.chem.mcgill.ca
CC:	linux-kernel@...r.kernel.org
Subject: Re: Memory not being reported

David Ronis wrote:
> I don't think this is a 64bit capable box.  Nonetheless, there are only
> 4G of memory, not more, and I still see 3G of it.

Can you post your dmesg output from bootup?

> 
> David
> 
> 
> 
> On Sat, 2009-01-24 at 02:37 -0600, Robert Hancock wrote:
>> David Ronis wrote:
>>> I'm running 2.6.28.1 on an i686 (slackware-12.1 for the most part) box.
>>> I recently added some extra memory, expanding from 2Gb to 4.  Everything
>>> works as expected except that not all of the memory seems to be seen.
>>>
>>> free returns:
>>>
>>>              total       used       free     shared    buffers
>>> cached
>>> Mem:       3374860    2099504    1275356          0      86612
>>> 1032024
>>> -/+ buffers/cache:     980868    2393992
>>> Swap:       497972          0     497972
>>>
>>>
>>> and cat /proc/meminfo gives:
>>>
>>> MemTotal:        3374860 kB
>>> MemFree:         1199184 kB
>>> Buffers:           86816 kB
>>> Cached:          1036240 kB
>>> SwapCached:            0 kB
>>> Active:          1375864 kB
>>>
>>> etc.
>>>
>>> On the other hand, user-space tools like lshw show the 4 1Gb DIMMS as
>>> does the BIOS configuration boot menu.
>>>
>>> One suspicion is that the configure option CONFIG_HIGHMEM4G=y
>>> should be unset and the CONFIG_HIGHMEM64G  should be.
>> Yes, it should be. However, if your chipset doesn't support remapping 
>> memory above the 4GB mark (some don't, and this is needed in this case 
>> because various IO areas use up some of the address space below 4GB) 
>> then it won't be possible to make use of any of that RAM.
>>
>> Note that when running with more than 4GB of RAM it's generally 
>> preferable to run a 64-bit kernel if the machine supports it.
>>
>>> Any help would be appreciated, as would a separate CC since I don't
>>> subscribe to the list.
>>>
>>> Thanks in advance
>>>
>>> David
>>>
> 
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