Messages in this thread | | | Date | Tue, 04 Nov 2014 14:48:47 -0700 | From | Jens Axboe <> | Subject | Re: [PATCH block/for-linus] blk-mq: make mq_queue_reinit_notify() freeze queues in parallel |
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On 2014-11-04 11:52, Tejun Heo wrote: > q->mq_usage_counter is a percpu_ref which is killed and drained when > the queue is frozen. On a CPU hotplug event, blk_mq_queue_reinit() > which involves freezing the queue is invoked on all existing queues. > Because percpu_ref killing and draining involve a RCU grace period, > doing the above on one queue after another may take a long time if > there are many queues on the system. > > This patch splits out initiation of freezing and waiting for its > completion, and updates blk_mq_queue_reinit_notify() so that the > queues are frozen in parallel instead of one after another. Note that > freezing and unfreezing are moved from blk_mq_queue_reinit() to > blk_mq_queue_reinit_notify(). > > Signed-off-by: Tejun Heo <tj@kernel.org> > Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> > --- > Christian, can you please verify that this resolves the latency issue > that you're seeing? Jens, can you please route this patch once > Christian confirms it?
Will queue up for 3.18.
-- Jens Axboe
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