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

Ming,

On Mon, 18 Feb 2019, Ming Lei wrote:

On Sun, Feb 17, 2019 at 08:17:05PM +0100, Thomas Gleixner wrote:

quoted

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.

quoted

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