Hey Willy,
- Interrupt steering needs to be controlled by block-mq instead of
the driver. It's pointless to have each driver implement its own
policies on interrupt steering, irqbalanced remains a source of
end-user frustration, and block-mq can change the queue<->cpu mapping
without the driver's knowledge.
I honestly don't think that block-mq is the right place to
*assign* interrupt steering. Not all HW devices are dedicated
to storage, take RDMA for example, a RNIC is shared by block
storage, networking and even user-space workloads so obviously
block-mq can't understand how a user wants to steer interrupts.
I think that block-mq needs to ask the device driver:
"what is the optimal queue index for cpu X?" and use it
while *someone* will be responsible for optimum interrupt
steering (can be the driver itself or user-space).
From some discussions I had with HCH I think he intends to
use the cpu reverse-mapping API to try and do what's described
above (if I'm not mistaken).
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