[NTLUG:Discuss] 64/32 question

[MadHat Unspecific]

Steve Baker wrote:
> Fred wrote:
>> What are the relative merits of running 32-bit Linux
>> on a dual core (or dual processor... is that the same 
>> thing?) computer vs 64-bit? 
>>   
> The really huge thing for me is that I can finally have more than 4 Gigs 
> of RAM with my 64 bit system.  Even on 32 bit systems, you can't 
> "really" have 4Gbytes of RAM without taking some performance hits - so 
> most people top out at 2 or 3 Gigs.  But with a 64 bit system you can 
> have a LOT more - if you need it.  The practical upshot of that is that 
> because the Kernel caches disk information into unused RAM, your access 
> to files that have been recently read gets a heck of a lot faster with 
> more RAM.

Can you provide any references on this?  Specifically that 4G on a 32bit
Linux system will experience performance hits.   I understand that you
have to have specific kernel settings to access all 4G, but once this is
done, are you saying there are performance hits?

I have seen people referencing it, but when looking at the actual PAE
kernel info, it says it supports up to 64G.

Linus talks about HIGHMEM and says it is usable for up to 4G, but he
considers it to be a waste.  But I thought HIGHMEM was a RedHatism and
not the same as PAE.
http://lkml.org/lkml/2007/11/15/423

Still googling.  I can find anecdotal evidence but nothing conclusive so
far.

-- 
MadHat (at) Unspecific.com
"The true man wants two things: danger and play.
 For that reason he wants woman, as the most dangerous plaything."
                          - Friedrich Nietzsche