linux-kernel - Re: Memory not being reported

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Date:	Sun, 25 Jan 2009 12:13:24 -0500
From:	David Ronis <ronis@...ispc.chem.mcgill.ca>
To:	Robert Hancock <hancockr@...w.ca>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Memory not being reported

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.

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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