Re: [PATCH V3] nvme-pci: allow unmanaged interrupts

[Ming Lei <ming.lei@redhat.com>]

On Tue, Jul 02, 2024 at 05:28:09PM +0200, Christoph Hellwig wrote:
> On Tue, Jul 02, 2024 at 12:20:30PM +0000, Lawrence Troup (ltroup) wrote:
> > Openshift needs the ability to dynamically move IRQs of all drivers away from a specific set of CPUs, at the point that an isolated workload starts running on those CPUs, and requires high performance guarantees, i.e. no HW interrupts to occur. To achieve this, dynamic setting of the smp_affinity for all drivers is used - at the moment, the NVME driver does not support this, so the NVME IRQs remain running on CPUs they should not be on, and so impact performance of the isolated workload.
> 
> Then you need to create a core kernel interface that moves all managed
> IRQs of these CPUs.

It is basically not doable or too hard since blk-mq queue mapping
depends on managed irq affinity.

> Without that you have a never ending whack a mole
> adding hacks to the drivers of the day that you care about.

So far, most popular SCSI hosts support the option via module parameter, and
the only remainder could be nvme-pci.


Thanks, 
Ming