linux-kernel - Re: Memory not being reported

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Date:	Thu, 22 Jan 2009 17:27:04 -0500
From:	Wakko Warner <wakko@...mx.eu.org>
To:	David Ronis <ronis@...ispc.chem.mcgill.ca>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Memory not being reported

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.

I'm running on 2.6.24.3 right now which is irrelevent.  Is your system
x86_64 capable?  This specific machine is not.  It's an older dual xeon 533mhz
fsb.

> free returns:
> 
>              total       used       free     shared    buffers
> cached
> Mem:       3374860    2099504    1275356          0      86612
> 1032024
> -/+ buffers/cache:     980868    2393992
> Swap:       497972          0     497972

             total       used       free     shared    buffers     cached
Mem:       4019196    1342956    2676240          0     405712     223672
-/+ buffers/cache:     713572    3305624
Swap:            0          0          0


> On the other hand, user-space tools like lshw show the 4 1Gb DIMMS as
> does the BIOS configuration boot menu.

lshw IIRC uses dmi information to obtain that information.

> One suspicion is that the configure option CONFIG_HIGHMEM4G=y
> should be unset and the CONFIG_HIGHMEM64G  should be.

# grep HIGH .config
# CONFIG_HIGH_RES_TIMERS is not set
# CONFIG_NOHIGHMEM is not set
# CONFIG_HIGHMEM4G is not set
CONFIG_HIGHMEM64G=y
CONFIG_HIGHMEM=y
# CONFIG_HIGHPTE is not set
# 

I see no reason not to use highmem 64gb  I've used it on several of my
systems, even ones that can't handle more than 2gb w/o problems.

One thing I have noticed (which is irrelevent to your question) is that I
see about 100mb less memory running a 64-bit kernel vs a 32-bit kernel on 2
systems (different brand of motherboard) and 4gb.  One was upgraded to 8gb;
32-bit shows about 8400000kb memory and running 64-bit shows about 8200000kb
memory.  Noone has answered my question as to why that is.

-- 
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