SMP affinity change
Dave Jones
davej at redhat.com
Fri Jun 9 19:44:09 UTC 2006
On Sat, Jun 10, 2006 at 06:45:22AM +1200, kjcsb wrote:
> I am running Fedora Core 4 2.6.16-1.2111 smp kernel on an aging 2 CPU Dell
> PowerEdge 2300. I am attempting to resolve some issues I'm having with a
> PCI device. I have changed many things (see posts to Asterisk users list
> entitled "Audio problems on Zap & SIP, local network, not IRQ related?")
> and am now trying to change the SMP affinity so that the PCI device (which
> is using IRQ20) is handled solely by CPU1:
> cat /proc/interrupts
> CPU0 CPU1
> 0: 54233 51707 IO-APIC-edge timer
> 1: 1 7 IO-APIC-edge i8042
> 8: 0 1 IO-APIC-edge rtc
> 9: 0 0 IO-APIC-level acpi
> 16: 47254 46402 IO-APIC-level megaraid
> 17: 2169 1325 IO-APIC-level aic7xxx, aic7xxx
> 18: 305 13 IO-APIC-level eth0
> 19: 0 0 IO-APIC-level uhci_hcd:usb1
> 20: 25694 20011 IO-APIC-level wctdm
> NMI: 0 0
> LOC: 105840 105584
> ERR: 0
> MIS: 0
>
> echo 2 > /proc/irq/20/smp_affinity
> cat /proc/irq/20/smp_affinity
> 00000002
>
> However I can see the interrupts for IRQ 20 are still incrementing on both
> CPUs. Indeed, after about 10 seconds...
> cat /proc/irq/20/smp_affinity
> 00000001
>
> On further investigation, the SMP affinity on ALL of the IRQs is set to
> 00000001. This implies that everything is handled by CPU0, which it clearly
> is not!
>
> I wonder if anyone has experienced anything similar or could offer some
> suggestions?
Your interrupts are being round-robin'd across CPUs by the
irqbalance service.
Dave
--
http://www.codemonkey.org.uk
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