Best kernel config for exactly 1GB ram

[Steve Bergman]

Hi,

I have just upgraded my athlon 1200 system to 1GB ram.  I am unclear as 
to how I should configure the kernel for this box.  The config.help says 
   to say no to "high memory support" if the kernel will not run on a 
machne with more than 1GB.  When I do this I notice that my available 
memory as reported by top is ~ 120MB less than if I say I want 4GB 
support.  I recall that linux reserves some of the address space for 
itself (I thought it was just 64MB).

What are the trade offs involved here?  Am I better off sacrificing a 
bit of the physical memory for reasons of efficiency elsewhere?  When I 
request support for up to 4GB, what exactly changes with respect to the 
visible virtual address space that apps see, etc?

This is a desktop machine, so it's not running Oracle or anything like 
that.  I seem to recall Linus mentioning that big databases tend to like 
the large (3GB) virtual address space.

Any enlightenment would be greatly appreciated.

Thanks,
Steve Bergman
[e-mail]