From: Bradley Chapman
Date: Sat Apr 28 2007 - 16:27:01 EST

After installing a second 512MB SODIMM into my laptop, I noticed that
my kernel only detected and used 896MB of the resulting 1GB,
and informed me that I needed to enable high memory in order to access
the remaining 127MB.

While doing so, I noticed that the help text stated that enabling high
memory (in my case, CONFIG_HIGHMEM4G) should only be done if the
system the kernel is running on has more than 1GB, but less than 4GB -
it said that systems with 1GB should leave it off, which resulted in
an eighth of the installed memory going missing. A bit more research
found a three year old thread on this list where it was stated that
enabling CONFIG_HIGHMEM4G sometimes slows the system down due to
sometimes undesirable changes to the way the kernel sets up the memory

Basically, all I want to know is whether or not enabling
CONFIG_HIGHMEM4G for a laptop that has exactly 1GB of RAM will result
in any performance degradation.



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