[PATCHv2] nvme-tcp: align I/O cpu with blk-mq mapping

[Kamaljit Singh]

On 19/06/2024 18:58, Sagi Grimberg wrote:
>>>> I see how you address multiple controllers falling into the same
>>>> mappings case in your patch.
>>>> You could have selected a different mq_map entry for each controller
>>>> (out of the entries that map to the qid).
>>>>
>>> Looked at it, but hadn't any idea how to figure out the load.
>>> The load is actually per-cpu, but we only have per controller
>>> structures.
>>> So we would need to introduce a per-cpu counter, detailing out the
>>> number of queues scheduled on that CPU.
>>> But that won't help with the CPU oversubscription issue; we still
>>> might have substantially higher number of overall queues than we have
>>> CPUs...
>>
>> I think that it would still be better than what you have right now:
>>
>> IIUC Right now you will have for all controllers (based on your example):
>> queue 1: using cpu 6
>> queue 2: using cpu 9
>> queue 3: using cpu 18
>>
>> But selecting a different mq_map entry can give:
>> ctrl1:
>> queue 1: using cpu 6
>> queue 2: using cpu 9
>> queue 3: using cpu 18
>>
>> ctrl2:
>> queue 1: using cpu 7
>> queue 2: using cpu 10
>> queue 3: using cpu 19
>>
>> ctrl3:
>> queue 1: using cpu 8
>> queue 2: using cpu 11
>> queue 3: using cpu 20
>>
>> ctrl4:
>> queue 1: using cpu 54
>> queue 2: using cpu 57
>> queue 3: using cpu 66
>>
>> and so on...
>
>Hey Hannes,
>
>Did you make progress with this one?

Sagi,
Looks like this change should also address the other NVMe/TCP issue that I had 
reported for WQ_UNBOUND, agree? If so, would this also be merged into 
6.8.xx branch as well?