On Fri, 30 Oct 2020 12:16:00 +0100 Paolo Abeni wrote:

Real-time setups try hard to ensure proper isolation between time
critical applications and e.g. network processing performed by the
network stack in softirq and RPS is used to move the softirq 
activity away from the isolated core.

If the network configuration is dynamic, with netns and devices
routinely created at run-time, enforcing the correct RPS setting
on each newly created device allowing to transient bad configuration
became complex.

These series try to address the above, introducing a new
sysctl knob: rps_default_mask. The new sysctl entry allows
configuring a systemwide RPS mask, to be enforced since receive 
queue creation time without any fourther per device configuration
required.

Additionally, a simple self-test is introduced to check the 
rps_default_mask behavior.

RPS is disabled by default, the processing is going to happen wherever
the IRQ is mapped, and one would hope that the IRQ is not mapped to the
core where the critical processing runs.

Would you mind elaborating further on the use case?