Re: Sarge not showing all RAM
On Thu, 2004-12-23 at 15:15, Jerome BENOIT wrote:
> Dave Ewart wrote:
> > On Thursday, 23.12.2004 at 13:39 +0000, Jerome BENOIT wrote:
> >
> >
> >>Hello List,
> >>
> >>I observed a similar behaviour on my Sarge laptop (Inspiron 8200): I
> >>have 1GB ram but /proc/mening shows (only) 905136 kB and the Gnome
> >>system monitor 884 MB.
> >>
> >>I have to say that my kernel is not 4GB enabled: so far I thought that
> >>1GB was smaller that 4GB.
>
> In fact, according to the help message provided by the kernel,
> 1GB is on the edge: so it is not so clear to me wether the kernel
> must be 4GB enabled.
>
> >
> >
> > There's something magic about that 905MB line - a 1GB RAM machine of
> > ours showed that amount as total RAM when on a non-4GB and non-64GB
> > kernel. Don't know why exactly it's 905MB, but that ties up with what I
> > saw. It's not sharing with AGP memory, because my system didn't have
> > that.
> >
> > Once upgraded to a 4GB kernel, the full 1GB was visible.
> >
> > Dave.
>
> I am rebuilding my kernel with this option.
>
> We will see,
> Jerome
There are three memory zones on x86 for linux
ZONE_DMA < 16 MB
ZONE_NORMAL 16-896 MB
ZONE_HIGHMEM > 896 MB
related to various hardware limitations. There's some interesting
discussions of this in 'Linux Kernel Development' by R. Love.
-peter
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