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From: Ming Lei <ming.lei@redhat.com>
To: Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	Daniel Wagner <dwagner@suse.de>, Wen Xiong <wenxiong@us.ibm.com>,
	John Garry <john.garry@huawei.com>
Subject: Re: [PATCH 2/2] nvme: pass BLK_MQ_F_NOT_USE_MANAGED_IRQ for fc/rdma/tcp/loop
Date: Wed, 30 Jun 2021 16:47:44 +0800	[thread overview]
Message-ID: <YNwvsNcTBu6yGW1o@T590> (raw)
In-Reply-To: <46fdb02d-8d71-d465-072d-5e8d6ec3601f@suse.de>

On Wed, Jun 30, 2021 at 10:15:46AM +0200, Hannes Reinecke wrote:
> On 6/29/21 9:49 AM, Ming Lei wrote:
> > All the 4 host drivers don't use managed irq for completing request, so
> > it is correct to pass the flag to blk-mq.
> > 
> > Secondly with this flag, blk-mq will help us dispatch connect request
> > allocated via blk_mq_alloc_request_hctx() to driver even though all
> > CPU in the specified hctx's cpumask are offline.
> > 
> How is this supposed to work?
> To my understanding, only cpus in the hctx cpumask are eligible to send I/O.
> So if all of these CPUs are offline, who exactly is submitting I/O?
> More to the point, which CPU will be submitting the connect request?

Please see __blk_mq_delay_run_hw_queue(), which will pass WORK_CPU_UNBOUND 
to kblockd_mod_delayed_work_on() for this situation.


Thanks,
Ming


  reply	other threads:[~2021-06-30  8:48 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-29  7:49 [PATCH 0/2] blk-mq: fix blk_mq_alloc_request_hctx Ming Lei
2021-06-29  7:49 ` [PATCH 1/2] blk-mq: not deactivate hctx if the device doesn't use managed irq Ming Lei
2021-06-29 12:39   ` Hannes Reinecke
2021-06-29 14:17     ` Ming Lei
2021-06-29 15:49   ` John Garry
2021-06-30  0:32     ` Ming Lei
2021-06-30  9:25       ` John Garry
2021-07-01  9:52       ` Christoph Hellwig
2021-06-29 23:30   ` Damien Le Moal
2021-06-30 18:58     ` Sagi Grimberg
2021-06-30 21:57       ` Damien Le Moal
2021-07-01 14:20         ` Keith Busch
2021-06-29  7:49 ` [PATCH 2/2] nvme: pass BLK_MQ_F_NOT_USE_MANAGED_IRQ for fc/rdma/tcp/loop Ming Lei
2021-06-30  8:15   ` Hannes Reinecke
2021-06-30  8:47     ` Ming Lei [this message]
2021-06-30  8:18 ` [PATCH 0/2] blk-mq: fix blk_mq_alloc_request_hctx Hannes Reinecke
2021-06-30  8:42   ` Ming Lei
2021-06-30  9:43     ` Hannes Reinecke
2021-06-30  9:53       ` Ming Lei
2021-06-30 18:59         ` Sagi Grimberg
2021-06-30 19:46           ` Hannes Reinecke
2021-06-30 23:59             ` Ming Lei
2021-07-01  8:00               ` Hannes Reinecke
2021-07-01  9:13                 ` Ming Lei
2021-07-02  9:47             ` Daniel Wagner

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