Can not set SMP affinity on kernels above 3.10.0-514

Can not set SMP affinity on kernels above 3.10.0-514

[Brian Atkinson]

I am currently receiving the following error whenever I go to adjust
the smp_affinity/smp_affinity_list files for IRQ's associated the
Samsung NVMe SDD PM1725a installed in a Dell PowerEdge R7425 server:

echo: write error: Input/output error

I have stopped/disabled irqbalance using the following:

systemctl stop irqbalance
systemctl disable irqbalance

However, I still get the Input/output error when I try and echo any
values into either the smp_affinity or smp_affinity_list files. What
is really peculiar about this, is I have no issues updating the values
in these files as long as I am on the stock kernel 3.10.0-514 that
came with CentOS 7.3; however, whenever I get this error on the
following kernels 3.10.0-862.11.6, 4.4.153-1, and 4.18.5-1. Since I am
only experiencing this issue in these newer kernels, I imagine there
is some setting I do not have set that is preventing me from updating
the SMP affinity values for the NVMe SDD's IRQ's. Has anyone else
experienced this issue and possibly know how to correct it?

-- 
Thank you,
Brian Atkinson

Can not set SMP affinity on kernels above 3.10.0-514

[Keith Busch]

On Wed, Sep 26, 2018@10:38:12AM -0600, Brian Atkinson wrote:
> I am currently receiving the following error whenever I go to adjust
> the smp_affinity/smp_affinity_list files for IRQ's associated the
> Samsung NVMe SDD PM1725a installed in a Dell PowerEdge R7425 server:
> 
> echo: write error: Input/output error
> 
> I have stopped/disabled irqbalance using the following:
> 
> systemctl stop irqbalance
> systemctl disable irqbalance
> 
> However, I still get the Input/output error when I try and echo any
> values into either the smp_affinity or smp_affinity_list files. What
> is really peculiar about this, is I have no issues updating the values
> in these files as long as I am on the stock kernel 3.10.0-514 that
> came with CentOS 7.3; however, whenever I get this error on the
> following kernels 3.10.0-862.11.6, 4.4.153-1, and 4.18.5-1. Since I am
> only experiencing this issue in these newer kernels, I imagine there
> is some setting I do not have set that is preventing me from updating
> the SMP affinity values for the NVMe SDD's IRQ's. Has anyone else
> experienced this issue and possibly know how to correct it?

NVMe interrupts are kernel managed, which isn't changeable from
user space.