Messages in this thread | | | Date | Mon, 17 Apr 2006 15:00:55 +0200 (CEST) | From | "Robert M. Stockmann" <> | Subject | irqbalance mandatory on SMP kernels? |
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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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