Re: [RFC] blk-mq: clean up the hctx restart

[Ming Lei]

On Thu, Aug 02, 2018 at 05:24:15PM +0000, Bart Van Assche wrote:
> On Fri, 2018-08-03 at 01:17 +0800, Ming Lei wrote:
> > Not mentioning big CPU utilization is consumed unnecessarily for iterating
> > over all queues even though there is only one active queue, is this fair from
> > system view?
> 
> I hope that someone will come up some day with a better solution than the
> list_for_each_entry_rcu_rr() loop. But as long as such a solution has not yet
> been found that loop should stay in order to preserve fair handling of large
> numbers of LUNs.

Again list_for_each_entry_rcu_rr() isn't fair for small number of active
queue in this case, because this way decreases IOPS a lot and consumes CPU
much just for checking all thousands of queues unnecessarily, even though 99%
of them are idle.

Thanks,
Ming