Re: blk-mq vs cpu hotplug performance (due to percpu_ref_put performance)

[Tejun Heo]

On Tue, Oct 28, 2014 at 09:20:55PM +0100, Christian Borntraeger wrote:
> I have not verified this, but I guess what happens is:
> hotplug
> -> notify
> -> blk_mq_queue_reinit_notify
> -> blk_mq_queue_reinit
> -> blk_mq_freeze_queue
> -> percpu_ref_kill
> -> percpu_ref_kill_and_confirm
> -> __percpu_ref_switch_to_atomic
> -> call_rcu_sched  

But call_rcu_sched() wouldn't show up as latency.  It's an async call
unlike synchronize_*().

Thanks.

-- 
tejun
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