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Old 11-07-2005, 02:35 PM   #1
Hammett
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Where RAM has gone??


Hi all!!

I've upgraded my PC by adding another 512Mb Kingston DDR RAM module. The bios recognises the new ram correctly (1Gb), and also does WinXP, but when it comes to linux... I see more than 100Mb dissapeared.

I've checked RAM memory with "cat /proc/meminfo | grep MemTotal" and the output is 906140 kB, so where's the rest of the RAM??

Thanks for your tips/suggestions/answers
 
Old 11-07-2005, 03:13 PM   #2
foo_bar_foo
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you have to enable highmem in the kernel to get that extra little bit
 
Old 11-07-2005, 03:32 PM   #3
SlackerLX
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Quote:
Originally posted by foo_bar_foo
you have to enable highmem in the kernel to get that extra little bit
Should you enable CONFIG_HIGHMEM for your 1 GB RAM system?

It is advised to not enable CONFIG_HIGHMEM in the kernel to utilize
the extra 128 MB you get for your 1 GB RAM system. I/O Devices cannot
directly address high memory from PCI space, so bounce buffers have to
be used. Plus the virtual memory management and paging costs come with
extra mappings. For details on bounce buffers, refer to Mel Gorman's
documentation (link below).

http://strasbourg.linuxfr.org/jl3/features-2.3-2.html

Last edited by SlackerLX; 11-07-2005 at 03:34 PM.
 
Old 11-07-2005, 04:31 PM   #4
Hammett
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Quote:
Originally posted by SlackerLX
Should you enable CONFIG_HIGHMEM for your 1 GB RAM system?

It is advised to not enable CONFIG_HIGHMEM in the kernel to utilize
the extra 128 MB you get for your 1 GB RAM system. I/O Devices cannot
directly address high memory from PCI space, so bounce buffers have to
be used. Plus the virtual memory management and paging costs come with
extra mappings. For details on bounce buffers, refer to Mel Gorman's
documentation (link below).

http://strasbourg.linuxfr.org/jl3/features-2.3-2.html
O.o wow....please, explain the same like if I was 4.... (AKA too complicated for me to understand). Although, I really appretiate your info, at least I know is not Linux's fault I don't see those 128Mb
 
Old 11-07-2005, 04:35 PM   #5
SlackerLX
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Quote:
Originally posted by Hammett
O.o wow....please, explain the same like if I was 4....
Normally, people do not spit into the well, from which they apt to drink...
 
Old 11-07-2005, 05:00 PM   #6
Hammett
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I quite expected something more constructive... I just simply want to UNDERSTAND what you said in your previous post.
 
Old 11-07-2005, 05:09 PM   #7
SlackerLX
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I'm sorry about being unclear
You need to recompile kernel for highmem usage. However, performance may be affected as you see from document I linked to..
Sorry again...
 
Old 11-07-2005, 11:03 PM   #8
foo_bar_foo
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Quote:
Originally posted by SlackerLX
Should you enable CONFIG_HIGHMEM for your 1 GB RAM system?

It is advised to not enable CONFIG_HIGHMEM in the kernel to utilize
the extra 128 MB you get for your 1 GB RAM system. I/O Devices cannot
directly address high memory from PCI space, so bounce buffers have to
be used. Plus the virtual memory management and paging costs come with
extra mappings. For details on bounce buffers, refer to Mel Gorman's
documentation (link below).

http://strasbourg.linuxfr.org/jl3/features-2.3-2.html

Nope this is old info and no longer true !
 
  


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