Re: [PATCH V7 4/6] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops

[Bart Van Assche]

On 10/16/17 23:38, Hannes Reinecke wrote:
> Again, these are just some pre-defined values to avoid I/O starvation
> when having several LUNs. _if_ we can guarantee I/O fairness between
> several (hundreds!) devices all sharing the same tagspace we wouldn't
> need these variables.

I think we already have two mechanisms for guaranteeing I/O fairness:
* Scsi_Host.starved_list for both the legacy SCSI core and scsi-mq.
* For scsi-mq, the active_queues counter in the blk-mq core. See also
  hctx_may_queue().

Bart.