RE: maximum memory capacity

From: Chiu, PCM (Peter) (P.C.M.Chiu_at_rl.ac.uk)
Date: 01/28/04

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    To: "'Joel Jaeggli'" <joelja@darkwing.uoregon.edu>, "'fedora-list@redhat.com'" <fedora-list@redhat.com>
Date: Wed, 28 Jan 2004 14:00:43 -0000

    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@darkwing.uoregon.edu]
    Sent: 27 January 2004 19:57
    To: 'fedora-list@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@redhat.com
    > [mailto:fedora-list-admin@redhat.com] On Behalf Of Joel Jaeggli
    > Sent: 26 January 2004 17:27
    > To: 'fedora-list@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@redhat.com
    > > [mailto:fedora-list-admin@redhat.com] On Behalf Of WipeOut
    > > Sent: 26 January 2004 15:02
    > > To: fedora-list@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@darkwing.uoregon.edu
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