FOLLOWUP -- 4 GB installed -- but Linux sees only 3 - Hardware

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Thread: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

  1. FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    I installed Fedora package kernel-PAE, and after booting to
    kernel-PAE, my system sees 4GB just fine. I am happy. Thanks for
    suggestions.

    i

  2. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    On Thu, 26 Apr 2007 18:10:57 -0500, Ignoramus3935 wrote:

    > I installed Fedora package kernel-PAE, and after booting to kernel-PAE,
    > my system sees 4GB just fine. I am happy. Thanks for suggestions.
    >
    > i


    You may want to consider installing 64 bit FC6. I always put 64 bit FC on
    my 4G machines. With 64 bit addressing individual programs can access all
    of memory, with PAE they are still limited to 3G. 4G is the boundary
    where you consider going 64 bit, above 4G it's a no brainer and below 4G
    there are no benefits. I don't think there is much of a downside to 64
    bits anymore, 64 bit Linux is very mature.

  3. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    General Schvantzkoph wrote:
    > On Thu, 26 Apr 2007 18:10:57 -0500, Ignoramus3935 wrote:
    >
    >> I installed Fedora package kernel-PAE, and after booting to kernel-PAE,
    >> my system sees 4GB just fine. I am happy. Thanks for suggestions.
    >>
    >> i

    >
    > You may want to consider installing 64 bit FC6. I always put 64 bit FC on
    > my 4G machines. With 64 bit addressing individual programs can access all
    > of memory, with PAE they are still limited to 3G. 4G is the boundary
    > where you consider going 64 bit, above 4G it's a no brainer and below 4G
    > there are no benefits. I don't think there is much of a downside to 64
    > bits anymore, 64 bit Linux is very mature.


    Does 64-bit Linux run on 32-bit machines (such as *86 machines)?

    Because I have 32-bit machine (Intel Xeon machine) and my processes get
    almost 4 GBytes each if they want them (most do not). My kernel .config file
    is like this (in part):

    # CONFIG_NOHIGHMEM is not set
    # CONFIG_HIGHMEM4G is not set
    CONFIG_HIGHMEM64G=y
    CONFIG_HIGHMEM=y
    CONFIG_HIGHPTE=y
    CONFIG_X86_PAE=y
    CONFIG_HIGHIO=y
    CONFIG_X86_4G=y <---<<<
    CONFIG_X86_SWITCH_PAGETABLES=y
    CONFIG_X86_4G_VM_LAYOUT=y
    CONFIG_X86_UACCESS_INDIRECT=y
    CONFIG_X86_HIGH_ENTRY=y

    4 GB kernel-space and 4 GB user-space virtual memory support
    CONFIG_X86_4G
    This option is only useful for systems that have more than 1 GB
    of RAM.

    The default kernel VM layout leaves 1 GB of virtual memory for
    kernel-space mappings, and 3 GB of VM for user-space applications.
    This option ups both the kernel-space VM and the user-space VM to
    4 GB.



    The cost of this option is additional TLB flushes done at
    system-entry points that transition from user-mode into kernel-mode.
    I.e. system calls and page faults, and IRQs that interrupt user-mode
    code. There's also additional overhead to kernel operations that copy
    memory to/from user-space. The overhead from this is hard to tell and
    depends on the workload - it can be anything from no visible overhead
    to 20-30% overhead. A good rule of thumb is to count with a runtime
    overhead of 20%.



    The upside is the much increased kernel-space VM, which more than
    quadruples the maximum amount of RAM supported. Kernels compiled with
    this option boot on 64GB of RAM and still have more than 3.1 GB of
    'lowmem' left. Another bonus is that highmem IO bouncing decreases,
    if used with drivers that still use bounce-buffers.



    There's also a 33% increase in user-space VM size - database
    applications might see a boost from this.



    But the cost of the TLB flushes and the runtime overhead has to be
    weighed against the bonuses offered by the larger VM spaces. The
    dividing line depends on the actual workload - there might be 4 GB
    systems that benefit from this option. Systems with less than 4 GB
    of RAM will rarely see a benefit from this option - but it's not
    out of question, the exact circumstances have to be considered.

    --
    .~. Jean-David Beyer Registered Linux User 85642.
    /V\ PGP-Key: 9A2FC99A Registered Machine 241939.
    /( )\ Shrewsbury, New Jersey http://counter.li.org
    ^^-^^ 07:55:01 up 69 days, 19:23, 3 users, load average: 4.19, 4.18, 4.09

  4. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    On Fri, 27 Apr 2007 12:12:15 +0000, Jean-David Beyer wrote:

    > General Schvantzkoph wrote:
    >> On Thu, 26 Apr 2007 18:10:57 -0500, Ignoramus3935 wrote:
    >>
    >>> I installed Fedora package kernel-PAE, and after booting to kernel-PAE,
    >>> my system sees 4GB just fine. I am happy. Thanks for suggestions.
    >>>
    >>> i

    >>
    >> You may want to consider installing 64 bit FC6. I always put 64 bit FC on
    >> my 4G machines. With 64 bit addressing individual programs can access all
    >> of memory, with PAE they are still limited to 3G. 4G is the boundary
    >> where you consider going 64 bit, above 4G it's a no brainer and below 4G
    >> there are no benefits. I don't think there is much of a downside to 64
    >> bits anymore, 64 bit Linux is very mature.

    >
    > Does 64-bit Linux run on 32-bit machines (such as *86 machines)?
    >

    Of course not.

  5. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    On Fri, 27 Apr 2007 00:08:11 +0000, General Schvantzkoph wrote:

    > On Thu, 26 Apr 2007 18:10:57 -0500, Ignoramus3935 wrote:
    >
    >> I installed Fedora package kernel-PAE, and after booting to kernel-PAE,
    >> my system sees 4GB just fine. I am happy. Thanks for suggestions.
    >>
    >> i

    >
    > You may want to consider installing 64 bit FC6.

    Afaik the op doesn't have 64 bit hardware.

  6. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    In comp.os.linux.misc Jean-David Beyer wrote:
    : Does 64-bit Linux run on 32-bit machines (such as *86 machines)?

    No of course not-- you need an x64 machine. Fortunately almost all
    modern PC's are x64, so unless your machine is more than a couple
    of years old you probably have 64-bit hardware.

    The Xeon you mention could be either 32 or 64 bit depending
    upon its vintage.

    Stan
    --
    Stan Bischof ("stan" at the below domain)
    www.worldbadminton.com

  7. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    On Fri, 27 Apr 2007 13:31:39 +0000 (UTC), stan@worldbadminton.com wrote:
    > In comp.os.linux.misc Jean-David Beyer wrote:
    >: Does 64-bit Linux run on 32-bit machines (such as *86 machines)?
    >
    > No of course not-- you need an x64 machine. Fortunately almost all
    > modern PC's are x64, so unless your machine is more than a couple
    > of years old you probably have 64-bit hardware.


    Did you mean to say "less than a couple of years old"?

    > The Xeon you mention could be either 32 or 64 bit depending
    > upon its vintage.


    You know, my mobo is limited to 4GB, so there is no point in upgrading
    to 64 bit -- all that would accomplish is wasting 4 more bytes per
    every pointer. I am happy with PAE. I am not anticipating processes
    that would take more than 3 GB either.

    Now, I am going to build a second colocated webserver, and for that, I
    would like to use 64 mit if it is as mature as advertised.

    i

  8. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    In comp.os.linux.misc Ignoramus32056 wrote:
    :> No of course not-- you need an x64 machine. Fortunately almost all
    :> modern PC's are x64, so unless your machine is more than a couple
    :> of years old you probably have 64-bit hardware.

    : Did you mean to say "less than a couple of years old"?

    umm- no -- note the sense of the logic:

    more than a couple of years old= machine may be 64 bit but not likely
    less than a couple of years old = machine is probably 64 bit

    anyhow- if you bought it recently it is probably 64 bit. Brand new now
    it is hard to find a 32 bit machine

    :> The Xeon you mention could be either 32 or 64 bit depending
    :> upon its vintage.

    : You know, my mobo is limited to 4GB, so there is no point in upgrading
    : to 64 bit -- all that would accomplish is wasting 4 more bytes per
    : every pointer. I am happy with PAE. I am not anticipating processes
    : that would take more than 3 GB either.

    then I would agree- stick with 32-bit OS

    : Now, I am going to build a second colocated webserver, and for that, I
    : would like to use 64 mit if it is as mature as advertised.

    It should be. 64 bit Windows works great, so 64-bit Linux should be
    quite solid also. But as you note , unless you have a fair amount of
    RAM there's no point.

    Stan
    --
    Stan Bischof ("stan" at the below domain)
    www.worldbadminton.com

  9. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    ["Followup-To:" header set to comp.os.linux.misc.]
    Ignoramus32056 staggered into the Black Sun and said:
    > stan@worldbadminton.com wrote:
    >> Jean-David Beyer wrote:
    >>> Does 64-bit Linux run on 32-bit machines (such as *86 machines)?

    >> No of course not-- you need an x64 machine. Fortunately almost all
    >> modern PCs are x64


    There are still a bunch of x86-32 laptops floating around.

    > I am happy with PAE. I am not anticipating processes that would take
    > more than 3 GB either. Now, I am going to build a second colocated
    > webserver, and for that, I would like to use 64 bit if it is as mature
    > as advertised.


    Linux x86-64 is stable and works well for *most* things. Server apps
    will be no problem. Most desktop apps work fine (except OOO, which runs
    fine under 32-bit emulation). The evil nvidia binary-only modules work
    fine. Compiling wmctrl on the x86-64 didn't work (some programmer
    thought long would always be 32 bits, or something.) The x86-32
    emulation libs worked well for every non-64bit program I tried *except*
    epsxe. So if you want to play old PSX games, you're sort of stuck with
    x86-32.

    How'd the LVM thing all work out, anyway?

    --
    "Cheer up, things could be worse." So I cheered up, and sure enough,
    things got worse.
    Matt G|There is no Darkness in Eternity/But only Light too dim for us to see

  10. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    stan@worldbadminton.com wrote:
    > In comp.os.linux.misc Jean-David Beyer wrote:
    > : Does 64-bit Linux run on 32-bit machines (such as *86 machines)?
    >
    > No of course not-- you need an x64 machine. Fortunately almost all
    > modern PC's are x64, so unless your machine is more than a couple
    > of years old you probably have 64-bit hardware.


    Early 2004.
    >
    > The Xeon you mention could be either 32 or 64 bit depending
    > upon its vintage.


    It is sort-of 32-bit, but has extra memory management, as does the chipset,
    so it can address 64 GBytes ram, although at most 4 GBytes per process.
    OTOH, the kernel seems to be able to cache 6 GBytes.

    They are this one: http://processorfinder.intel.com/det...px?sSpec=SL73P
    >
    > Stan



    --
    .~. Jean-David Beyer Registered Linux User 85642.
    /V\ PGP-Key: 9A2FC99A Registered Machine 241939.
    /( )\ Shrewsbury, New Jersey http://counter.li.org
    ^^-^^ 11:10:01 up 69 days, 22:38, 3 users, load average: 4.23, 4.18, 4.11

  11. Re: FOLLOWUP -- 4 GB installed -- but Linux sees only 3

    ["Followup-To:" header set to comp.os.linux.misc.]

    On 2007-04-27, stan@worldbadminton.com wrote:
    >
    > anyhow- if you bought it recently it is probably 64 bit. Brand new now
    > it is hard to find a 32 bit machine


    True, but there are still plenty of eminently usable 32bit machines out
    there. I support at least 10 of them.

    > It should be. 64 bit Windows works great, so 64-bit Linux should be
    > quite solid also. But as you note , unless you have a fair amount of
    > RAM there's no point.


    64bit linux is as solid as 32bit. I support at least 5 64bit machines,
    and they all work fine. (IIRC all of these machines have at least 8GB
    of memory, so I really want a 64-bit linux, not 32bit.)

    --keith

    --
    kkeller-usenet@wombat.san-francisco.ca.us
    (try just my userid to email me)
    AOLSFAQ=http://www.therockgarden.ca/aolsfaq.txt
    see X- headers for PGP signature information


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