[NTLUG:Discuss] > 960 meg ram -- HIMEM kernel option -vs- 64bit Linux OS...

[Chris Cox]

Richard Geoffrion wrote:
> What *IS* the deal with having more than XX amount of RAM in a linux 
> server?   You can have 2 gig but it won't use more than 960 Meg unless 
> you turn on the HIMEM option...in which case there will be 
> incompatibilities.  --OR-- you can just load up a 64bit Kernel (Ubuntu 
> 64, SLAMD64..etc) and then you won't have those 32bit memory 
> limitations---but you'll have other compatibility issues..
> 
> 
> So which is it?  Do I stick with say... Slackware 10.2-current (a 32 bit 
> OS) and compile in the HIMEM option or do I take the plunge and go to a 
> 64bit OS (www.slamd64.com) where I might have 'other' issues?
> 
> What ARE the respective issues?
> 

Uh... none AFAIK.  SUSE compiles their kernels with HIGHMEM and
HIGHMEM4G... you can get HIGHMEM64G versions as well.

What incompatibilities??  I haven't seen any.

Obviously there's are some hits if you compile for 64G on Intel 32bit.
But it's nice when you have to use an Intel box with large memory.

But AFAIK, it's just a perf hit primarily for PAE on large memory
Intel.

Also, I do run 64bit SUSE as well.. the only issues in the application
space.  But SUSE does a good job of allowing mixed 64bit and 32bit
binaries on the system (without the chroot trick).  I use a 32bit
set of media players for example so I can use the w32codecs.