Re: [patch v6 7/7] genirq/affinity: Add support for non-managed affinity sets

[Thomas Gleixner]

Ming,

On Mon, 18 Feb 2019, Ming Lei wrote:
> On Sun, Feb 17, 2019 at 08:17:05PM +0100, Thomas Gleixner wrote:
> > I don't see how that would break blk-mq. The unmanaged set is not used by
> > the blk-mq stuff, that's some driver internal voodoo. So blk-mq still gets
> > a perfectly spread and managed interrupt set for the queues.
> 
> >From the discussion above, the use case is for megaraid_sas. And one of the
> two interrupt sets(managed and non-managed) will be chosen according to
> workloads runtime.
> 
> Each interrupt set actually defines one blk-mq queue mapping, and the
> queue mapping needs to respect the rule I mentioned now. However,
> non-managed affinity can be changed to any way anytime by user-space.
> 
> Recently HPSA tried to add one module parameter to use non-managed
> IRQ[1].
> 
> Also NVMe RDMA uses non-managed interrupts, and at least one CPU hotplug
> issue is never fixed yet[2]. 
> 
> [1] https://marc.info/?t=154387665200001&r=1&w=2
> [2] https://www.spinics.net/lists/linux-block/msg24140.html

Interesting. I misread the description which megasas folks provided
then. I'll drop that patch and get the other lot merged. Thanks for your
work and help with that!

Thanks,

	tglx