Memory Usage in a IBM Server running RHEL 3 - Redhat

This is a discussion on Memory Usage in a IBM Server running RHEL 3 - Redhat ; The following is the top output from a IBM eServer 325 running on a AMD Opteron Server. The Server is running Red Hat Enterprise Linux 3. The server came loaded with 3GB of RAM and upon constant analysis I found ...

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Thread: Memory Usage in a IBM Server running RHEL 3

  1. Memory Usage in a IBM Server running RHEL 3

    The following is the top output from a IBM eServer 325 running on a
    AMD Opteron Server. The Server is running Red Hat Enterprise Linux 3.
    The server came loaded with 3GB of RAM and upon constant analysis I
    found that it using less than 1GB of RAM while it shows a iowait of
    94%. Kindly let me know how to resolve the issue.

    08:07:30 up 1 day, 17:03, 1 user, load average: 4.46, 3.45, 3.63
    189 processes: 187 sleeping, 2 running, 0 zombie, 0 stopped
    CPU states: cpu user nice system irq softirq iowait
    idle
    total 2.5% 0.0% 2.9% 0.0% 0.3% 94.0%
    0.0%
    Mem: 3094216k av, 768436k used, 2325780k free, 0k shrd,
    160108k buff
    322528k active, 102208k inactive
    Swap: 6289408k av, 0k used, 6289408k free
    143228k cached


    And I also noticed a couple of errors as shown below in the dmesg
    output

    IO APIC #2......
    ..... register #00: 02000000
    ........ : physical APIC id: 02
    ........ : Delivery Type: 0
    ........ : LTS : 0
    ..... register #01: 00030011
    ........ : max redirection entries: 0003
    An unexpected IO-APIC was found. If this kernel release is less than
    three months old please report this to linux-smp@vger.kernel.org
    ........ : PRQ implemented: 0
    ........ : IO APIC version: 0011
    ..... register #02: 00000000
    ........ : arbitration: 00
    ..... IRQ redirection table:
    NR Log Phy Mask Trig IRR Pol Stat Dest Deli Vect:
    00 001 01 1 1 0 1 0 1 1 B9
    01 001 01 1 1 0 1 0 1 1 C1
    02 001 01 1 1 0 1 0 1 1 C9
    03 000 00 1 0 0 0 0 0 0 00

    IO APIC #3......
    ..... register #00: 03000000
    ........ : physical APIC id: 03
    ........ : Delivery Type: 0
    ........ : LTS : 0
    ..... register #01: 00030011
    ........ : max redirection entries: 0003
    An unexpected IO-APIC was found. If this kernel release is less than
    three months old please report this to linux-smp@vger.kernel.org
    ........ : PRQ implemented: 0
    ........ : IO APIC version: 0011
    ..... register #02: 00000000
    ........ : arbitration: 00
    ..... IRQ redirection table:
    NR Log Phy Mask Trig IRR Pol Stat Dest Deli Vect:
    00 000 00 1 0 0 0 0 0 0 00
    01 000 00 1 0 0 0 0 0 0 00
    02 000 00 1 0 0 0 0 0 0 00
    03 000 00 1 0 0 0 0 0 0 00

  2. Re: Memory Usage in a IBM Server running RHEL 3

    On Sun, 13 Mar 2005 08:22:59 -0800, Samuel Victor wrote:

    > The following is the top output from a IBM eServer 325 running on a
    > AMD Opteron Server. The Server is running Red Hat Enterprise Linux 3.
    > The server came loaded with 3GB of RAM and upon constant analysis I
    > found that it using less than 1GB of RAM while it shows a iowait of
    > 94%. Kindly let me know how to resolve the issue.
    >


    Is CONFIG_X86_4G set in the /boot/config file?

  3. Re: Memory Usage in a IBM Server running RHEL 3

    The CONFIG_X86_4G value is not set in the config file.

    Jonathan Edwards wrote in message news:...
    > On Sun, 13 Mar 2005 08:22:59 -0800, Samuel Victor wrote:
    >
    > > The following is the top output from a IBM eServer 325 running on a
    > > AMD Opteron Server. The Server is running Red Hat Enterprise Linux 3.
    > > The server came loaded with 3GB of RAM and upon constant analysis I
    > > found that it using less than 1GB of RAM while it shows a iowait of
    > > 94%. Kindly let me know how to resolve the issue.
    > >

    >
    > Is CONFIG_X86_4G set in the /boot/config file?


  4. Re: Memory Usage in a IBM Server running RHEL 3

    [ Followup-To --> comp.os.linux.redhat,comp.os.linux.setup ]

    In comp.os.linux.setup Samuel Victor :
    > The following is the top output from a IBM eServer 325 running on a
    > AMD Opteron Server. The Server is running Red Hat Enterprise Linux 3.
    > The server came loaded with 3GB of RAM and upon constant analysis I
    > found that it using less than 1GB of RAM while it shows a iowait of
    > 94%. Kindly let me know how to resolve the issue.


    First of, are you running the latest patches + update kernel
    available from rhn? 'uname -r' should tell concerning the kernel.

    > 08:07:30 up 1 day, 17:03, 1 user, load average: 4.46, 3.45, 3.63
    > 189 processes: 187 sleeping, 2 running, 0 zombie, 0 stopped
    > CPU states: cpu user nice system irq softirq iowait
    > idle
    > total 2.5% 0.0% 2.9% 0.0% 0.3% 94.0%
    > 0.0%


    Might be just one or another cron/anacron job left over, updatedb
    or so, perhaps stuck on a nfs mount? Check what processes 'ps
    faux' are most likely for the problem.

    > And I also noticed a couple of errors as shown below in the dmesg
    > output.


    Again, there have been numerous kernel updates for RHEL 3.0, the
    problem you are seeing might be resolved some time ago, but alas
    without knowing 'uname -r' your kernel version, hard to tell.

    BTW
    Please don't post a problem completely unrelated to sendmail, to
    the sendmail ng, thx.

    --
    Michael Heiming (X-PGP-Sig > GPG-Key ID: EDD27B94)
    mail: echo zvpunry@urvzvat.qr | perl -pe 'y/a-z/n-za-m/'
    #bofh excuse 288: Hard drive sleeping. Let it wake up on
    it's own...

  5. Re: Memory Usage in a IBM Server running RHEL 3

    On Tue, 15 Mar 2005 00:24:40 -0800, Samuel Victor wrote:

    > The CONFIG_X86_4G value is not set in the config file.
    >
    > Jonathan Edwards wrote in message news:...
    >> On Sun, 13 Mar 2005 08:22:59 -0800, Samuel Victor wrote:
    >>
    >> > The following is the top output from a IBM eServer 325 running on a
    >> > AMD Opteron Server. The Server is running Red Hat Enterprise Linux 3.
    >> > The server came loaded with 3GB of RAM and upon constant analysis I
    >> > found that it using less than 1GB of RAM while it shows a iowait of
    >> > 94%. Kindly let me know how to resolve the issue.
    >> >

    >>
    >> Is CONFIG_X86_4G set in the /boot/config file?


    You might want to try rebuilding the kernel with it set. Here is the
    descrption of the option:

    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.




  6. Re: Memory Usage in a IBM Server running RHEL 3

    Samuel Victor wrote:
    > The following is the top output from a IBM eServer 325 running on a
    > AMD Opteron Server. The Server is running Red Hat Enterprise Linux 3.
    > The server came loaded with 3GB of RAM and upon constant analysis I
    > found that it using less than 1GB of RAM while it shows a iowait of
    > 94%. Kindly let me know how to resolve the issue.


    How about telling us what issue you're trying to resolve... You have
    excess memory, excess CPU, and your i/o system is heavily loaded. If you
    want a quick fix, dowload setiathome and run that, it will use up the
    CPU and memory, and the waitio will go away.

    On the other hand, if you want more useful advice, how about a more
    useful question? What application are you running, and is it actually
    performing poorly, or what? What kernel, what distro, what disk and
    network hardware?

    --
    -bill davidsen (davidsen@tmr.com)
    "The secret to procrastination is to put things off until the
    last possible moment - but no longer" -me

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