maximum memory capacity

[Chiu, PCM (Peter)]

Hi Joel/Jos,

It is a per process access. 

If I can summarise like this:
a. 3GB per process memory access is still the limit for RH9, FC1 and RHES 3.

b. The 2.4 kernels can support up to 64GB memory.
 
c. RH9 and presumably RHES 3 as well automatically produce bigmem kernel to
support
   memory size over 4GB.

d. FC1 will require a manual step to tune up the kernel to support memory
size > 4GB.

e. 4GB memory or more may incure 4-6% additional performance overhead.

f. 2.6 kernels support up to 512GB memory, and 

g. Opterons in theory can support up to 1TB of virtual memory.

Peter

-----Original Message-----
From: Joel Jaeggli [mailto:joelja at darkwing.uoregon.edu] 
Sent: 27 January 2004 19:57
To: 'fedora-list at redhat.com'
Cc: Chiu, PCM (Peter) 
Subject: RE: maximum memory capacity


On Tue, 27 Jan 2004, Chiu, PCM (Peter)  wrote:

> Thanks, Joel,
> 
> My experience on a dual Xeon 2.4GHz cpus, 6GB memory with RH 9 and 
> bigmem kernel allows us to access physical memory size up to 3GB but 
> not beyond.

on a per process basis or overall? it should be work given what's 
documented, individual processes will never exceed 3GB though... 
 
> Do you know if it is possible to do so under FC1, or RHES, or none of 
> them?

fc1 has no bigmem kernels... you you get to rebuilt the normal one with 
64GB supported turned on... RHES you get support for that from the 
vendor... ymmv

> Peter
> 
> -----Original Message-----
> From: fedora-list-admin at redhat.com 
> [mailto:fedora-list-admin at redhat.com] On Behalf Of Joel Jaeggli
> Sent: 26 January 2004 17:27
> To: 'fedora-list at redhat.com'
> Subject: RE: maximum memory capacity
> 
> 
> On Mon, 26 Jan 2004, Chiu, PCM (Peter)  wrote:
> 
> > Thanks, my understanding on 32-bit based platforms, the limitation 
> > is
> > 4GB.
> 
> linux on x86 can support up to 64GB of ram... address space is 4GB so 
> not all of it gets permently mapped... kernels aren't generally 
> compiled for 64GB because the address extensions will prevent the 
> kernel from booting on cpu's that don't support it... that said you'll 
> have a fair performance tradeoff to consider with more than 4GB of ram 
> (3%-6% more overhead depending on the application). also the most 
> memory an individual process can use is 3GB of ram.
>  
> > Opterons or Itanium can lift this limitation.
> 
> The opteron's long mode supports 1TB of addressable memory the current
> 2.6.X support 512GB as I understand it... populating an opteron mainboard 
> with more than 16-20GB of ram (tyan s4880 has 10 dimm sockets) is left as 
> an exerercise for the reader.
> 
> > But not sure what their latest status.
> > 
> > Peter
> > -----Original Message-----
> > From: fedora-list-admin at redhat.com
> > [mailto:fedora-list-admin at redhat.com] On Behalf Of WipeOut
> > Sent: 26 January 2004 15:02
> > To: fedora-list at redhat.com
> > Subject: Re: maximum memory capacity
> > 
> > 
> > Chiu, PCM (Peter) wrote:
> > 
> > >Can anyone tell me the maximum physical and virtual memory sizes 
> > >supported under FC1?
> > >
> > >I am trying to work out the technical differences between RHES and
> > >FC1
> > >to enable us to choose the appropriate version to use.  I am aware of 
> > >the initial licenses and maintenance issues.
> > >
> > >Many Thanks.
> > >
> > >Peter
> > >
> > >
> > >  
> > >
> > Something says to me that the standard Fedora kernel is setup for 
> > 4GB
> > (I
> > amy be wrong).. But there is nothing stopping you building a kernel for 
> > larger amounts of memory..
> > 
> > later..
> > 
> > 
> > 
> 
> 

-- 
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Joel Jaeggli  	       Unix Consulting 	       joelja at darkwing.uoregon.edu

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