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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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