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

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

On Tue, Jul 02, 2024 at 01:50:02PM +0200, Christoph Hellwig wrote:
> On Tue, Jul 02, 2024 at 06:41:12PM +0800, Ming Lei wrote:
> > From: Keith Busch <kbusch@kernel.org>
> > 
> > People _really_ want to control their interrupt affinity in some
> > cases, such as Openshift with Performance profile, in which each
> > irq's affinity is completely specified from userspace. Turns out
> > that 'isolcpus=managed_irqs' isn't enough.
> > 
> > Add module parameter to allow unmanaged interrupts, just as some
> > SCSI drivers are doing.
> 
> Same as before: hell no.  We can't just add hacky global kernel
> parameters everywhere.  We need the cpu isolation infrastructure to
> work properly instead of piling hacks of hacks in every relevant driver.

Per my understanding, here cpu isolation infrastructure can't work for
Openshift, in which IO workload can be run on applications which are executed
on isolated CPUs, meantime userspace do expect that interrupts can be
triggered on user-specified CPU cores only in controllable way.  

Marcelo and Lawrence may have more input in this area.

Also irq allocation really belongs to device & driver stuff, how can that be
hack? We even may not abstract public API in block layer for handling
irq related thing.


Thanks, 
Ming