Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Tim Allingham <deserted@westnet.com.au>]

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On Sun, 2007-07-29 at 09:39 +1000, Tim Allingham wrote:
> On Sat, 2007-07-28 at 20:28 -0300, Daniel van Ham Colchete wrote:
> > Hello everyone!!!
> > 
> > May be somebody can shed some light here... I'm building a server here
> > with 4GB of RAM memory. The fact is, if I boot with mem=3072M
> > everything goes as fast as it should but I'm not using 1GB of memory.
> > If I don't put the mem option, Linux will see 4GB of memory available
> > but it will be damn slow (really). 
> > 
> > To make Linux recognize 4 gigs of memory I had to activate
> > HIGHMEM=64GB, otherwise it only recognizes 3279MB (but it is fast).
> > 
> > My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard is
> > Intel. I'm running Gentoo at 32bits mode and the kernel version is
> > 2.6.20-gentoo-r8.
> > 
> > Any lights would be very appreciated.
> > 
> > Best regards,
> > Daniel Colchete
> 
> I don't actually run 4GB of RAM in any of my intel systems, so I can't
> comment from experience, however my suspicion would be the overhead
> introduced from PAE, which (at least on older kernels) requires some
> processing overhead to utilise.  Are you able to try a 64-bit install to
> determine if this is the case?
> 
> Regards,
> 
> Tim Allingham
> Email:Tim@DataFirst-IT.com.au

just to add, this page gives a reasonable explanation of the problems
with 32-bit OS's trying to address large RAM volumes

http://www.dansdata.com/askdan00015.htm

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