[LSF/MM/BPF BOF] Userspace command abouts

[Sagi Grimberg]

>>> I'm not up to speed on how CDL is defined, but I'm unclear how CDL at
>>> the queue level would cause the host to open more queues?
> 
> Because each CDL class would need its own submission queue in that scheme. They
> can all share a single completion queue, so this scheme doesn't necassarily
> increase the number of interrupt vectors.

Ah, that is less desirable I think, Although we can already do
multiple queue maps, I think that the proliferation of queues is
harmful in the long run.

>>> Another question, does CDL have any relationship with NVMe "Time Limited
>>> Error Recovery"? where the host can set a feature for timeout and
>>> indicate if the controller should respect it per command?
>>>
>>> While this is not a full-blown every queue/command has its own timeout,
>>> it could address the original use-case given by Hannes. And it's already
>>> there.
>> I guess that is the NVMe version of CDLs; can you give me a reference for
>> it?
> 
> They're not the same. TLER starts timing after a command experiences a
> recoverable error, where CDL is an end-to-end timing for all commands.

Ah, ok. I didn't realize that TLER starts after an error.