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Hardware Interrupt Balancing

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From: James Lamanna
Subject: Hardware Interrupt Balancing
Date: Wednesday, March 24, 2010 - 6:11 pm

Hi,
I have a Dual Xeon (single core each w/HT) machine and I noticed the
other day that interrupts are not
being balanced across the 2 processors:

          CPU0       CPU1       CPU2       CPU3
  0:        306          0          0 3254413993    IO-APIC-edge  timer
  1:          0          0          0      13468    IO-APIC-edge  i8042
  8:          0          0          0          3    IO-APIC-edge  rtc
  9:          0          0          0          0   IO-APIC-level  acpi
 12:          0          0          0          4    IO-APIC-edge  i8042
169:          0          0          0          0   IO-APIC-level  uhci_hcd:usb2
177:          0          0          0   16743166   IO-APIC-level  ata_piix
185:          0          0          0          1   IO-APIC-level  ehci_hcd:usb1
193:          0          0          0          0   IO-APIC-level  uhci_hcd:usb3
201:          0          0          0 1867922172   IO-APIC-level  eth0
209:          0          0          0 3254690559   IO-APIC-level  wct4xxp
NMI:          1          0          0          0
LOC: 3255261535 3255261540 3255261549 3255220504
ERR:          0
MIS:          0

However the cpu_affinity of say, wct4xxp is:
# cat /proc/irq/209/smp_affinity
0000000f

Is there something (CPU Hotplug?) preventing the hardware interrupts
from being balanced across both CPUs?
The kernel version is 2.6.18 (i686) (this is an older machine that is
a PSTN<->SIP gateway).

Thanks.

-- James

Please CC me for I am not subscribed.
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Messages in current thread:
Hardware Interrupt Balancing, James Lamanna, (Wed Mar 24, 6:11 pm)
Re: Hardware Interrupt Balancing, Alejandro Riveira =? ..., (Thu Mar 25, 3:36 am)
Re: Hardware Interrupt Balancing, James Lamanna, (Mon Mar 29, 1:14 pm)