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SubjectRe: [IRQ] IRQ affinity not working properly?
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On Wed, Apr 21 2021 at 09:31, Nitesh Narayan Lal wrote:
> On 3/28/21 2:45 PM, Thomas Gleixner wrote:
>> On Fri, Jan 29 2021 at 13:17, Chris Friesen wrote:
>>> I have a CentOS 7 linux system with 48 logical CPUs and a number of
>
> <snip>
>
>>> 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 IRQ subsystem is not respecting the
>>> configured SMP affinity for the interrupt in question. I've also seen
>>> the same behaviour with igb interrupts.
>> No it's not expected. Do you see the same behaviour with a recent
>> mainline kernel, i.e. 5.10 or 5.11?
>>
>>
> Jesse pointed me to this thread and apologies that it took a while for me
> to respond here.
>
> I agree it will be interesting to see with which kernel version Chris is
> reproducing the issue.

And the output of

/proc/irq/$NUMBER/smp_affinity_list
/proc/irq/$NUMBER/effective_affinity_list

> Initially, I thought that this issue is the same as the one that we have
> been discussing in another thread [1].
>
> However, in that case, the smp affinity mask itself is incorrect and doesn't
> follow the default smp affinity mask (with irqbalance disabled).

That's the question...

Thanks,

tglx

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