[Intel-wired-lan] IRQ affinity not working properly?
Chris Friesen
chris.friesen at windriver.com
Fri Jan 29 15:41:09 UTC 2021
Hi,
I have a CentOS 7 linux system with 48 logical CPUs and a number of
Intel NICs running the i40e driver. It was booted with
irqaffinity=0-1,24-25 in the kernel boot args, resulting in
/proc/irq/default_smp_affinity showing "0000,03000003". CPUs 2-11 are
set as "isolated" in the kernel boot args. The irqbalance daemon is not
running.
The iavf driver is 3.7.61.20 and the i40e driver is 2.10.19.82
The problem I'm seeing is that /proc/interrupts shows iavf interrupts on
other CPUs than the expected affinity. For example, here are some
interrupts on CPU 4 where I would not expect to see any interrupts given
that "cat /proc/irq/<NUM>/smp_affinity_list" reports "0-1,24-25" for all
these interrupts. (Sorry for the line wrapping.)
cat /proc/interrupts | grep -e CPU -e 941: -e 942: -e 943: -e 944: -e
945: -e 961: -e 962: -e 963: -e 964: -e 965:
CPU0 CPU1 CPU2 CPU3 CPU4 CPU5
941: 0 0 0 0 28490 0
IR-PCI-MSI-edge iavf-0000:b5:03.6:mbx
942: 0 0 0 0 333832 0
IR-PCI-MSI-edge iavf-net1-TxRx-0
943: 0 0 0 0 300842 0
IR-PCI-MSI-edge iavf-net1-TxRx-1
944: 0 0 0 0 333845 0
IR-PCI-MSI-edge iavf-net1-TxRx-2
945: 0 0 0 0 333822 0
IR-PCI-MSI-edge iavf-net1-TxRx-3
961: 0 0 0 0 28492 0
IR-PCI-MSI-edge iavf-0000:b5:02.7:mbx
962: 0 0 0 0 435608 0
IR-PCI-MSI-edge iavf-net1-TxRx-0
963: 0 0 0 0 394832 0
IR-PCI-MSI-edge iavf-net1-TxRx-1
964: 0 0 0 0 398414 0
IR-PCI-MSI-edge iavf-net1-TxRx-2
965: 0 0 0 0 192847 0
IR-PCI-MSI-edge iavf-net1-TxRx-3
There were IRQs coming in on the "iavf-0000:b5:02.7:mbx" interrupt at
roughly 1 per second without any traffic, while the interrupt rate on
the "iavf-net1-TxRx-<X>" seemed to be related to traffic.
Is this expected? It seems like the iavf and/or the i40e aren't
respecting the configured SMP affinity for the interrupt in question.
Anyone have any ideas?
Thanks,
Chris
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