Re: [PATCH 0/2] blk-mq: fix blk_mq_alloc_request_hctx

Sagi Grimberg
2021-06-30T18:59:36Z

>>>> Shouldn't we rather modify the tagset to only refer to the current online
>>>> CPUs _only_, thereby never submit a connect request for hctx with only
>>>> offline CPUs?
>>>
>>> Then you may setup very less io queues, and performance may suffer even
>>> though lots of CPUs become online later.
>>> ;
>> Only if we stay with the reduced number of I/O queues. Which is not what I'm
>> proposing; I'd rather prefer to connect and disconnect queues from the cpu
>> hotplug handler. For starters we could even trigger a reset once the first
>> cpu within a hctx is onlined.
>
> Yeah, that need one big/complicated patchset, but not see any advantages
> over this simple approach.

I tend to agree with Ming here.