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    Subjectirqbalance mandatory on SMP kernels?

    Hi,

    I noticed that the latest editions of RedHat EL 4.3 and direct
    descendants today need a program called irqbalance to activate
    true SMP IRQ load balancing for your machine's hardware.

    If one boots a SMP kernel (2.4.xx or 2.6.xx) kernel on a machine
    which either has 2 or more physical CPU's (also dual-core CPU's)
    , and one does not start up the irqbalance util from the
    kernel-utils package ( see e.g.

    ftp://ftp.nluug.nl/pub/os/Linux/distr/RedHat/ftp/redhat/linux/updates/enterprise/4Desktop/en/os/SRPMS/kernel-utils-2.4-13.1.80.src.rpm

    ) Then basicly your SMP kernel falls back to a ordinary MP kernel and
    we see this happening :

    [jackson:stock]:(/usr/src/linux)$ cat /proc/interrupts
    CPU0 CPU1
    0: 3139568 0 IO-APIC-edge timer
    1: 8923 0 IO-APIC-edge i8042
    3: 10 0 IO-APIC-edge serial
    4: 37 0 IO-APIC-edge serial
    8: 0 0 IO-APIC-edge rtc
    9: 240 0 IO-APIC-level acpi
    12: 75316 0 IO-APIC-edge i8042
    14: 64291 0 IO-APIC-edge ide0
    15: 64291 0 IO-APIC-edge ide1
    16: 235408 0 IO-APIC-level HiSax, nvidia
    17: 15823 0 IO-APIC-level libata, AMD AMD8111
    19: 241 0 IO-APIC-level ohci_hcd, ohci_hcd, ohci1394
    24: 50761 0 IO-APIC-level eth0
    NMI: 89 28
    LOC: 3139042 3139125
    ERR: 0
    MIS: 0
    [jackson:stock]:(/usr/src/linux)$

    Only when firing up the irqbalance util at boot time will activate
    true SMP, distributing IRQ's across CPU's. Is this on purpose?
    Because afaik a Linux SMP kernel, 2.4.xx or 2.6.xx should always
    result in distributed IRQ loads across CPU's.

    Regards,

    Robert
    --
    Robert M. Stockmann - RHCE
    Network Engineer - UNIX/Linux Specialist
    crashrecovery.org stock@stokkie.net

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