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From: Ming Lei <ming.lei@redhat.com>
To: John Garry <john.garry@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Keith Busch <keith.busch@intel.com>
Subject: Re: [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug
Date: Tue, 29 Oct 2019 09:50:09 +0800	[thread overview]
Message-ID: <20191029015009.GD22088@ming.t460p> (raw)
In-Reply-To: <a5e25466-c4db-c254-be37-45a9ca85851c@huawei.com>

On Mon, Oct 28, 2019 at 11:55:42AM +0000, John Garry wrote:
> > > 
> > > For the SCSI commands which timeout, I notice that
> > > scsi_set_blocked(reason=SCSI_MLQUEUE_EH_RETRY) was called 30 seconds
> > > earlier.
> > > 
> > >   scsi_set_blocked+0x20/0xb8
> > >   __scsi_queue_insert+0x40/0x90
> > >   scsi_softirq_done+0x164/0x1c8
> > >   __blk_mq_complete_request_remote+0x18/0x20
> > >   flush_smp_call_function_queue+0xa8/0x150
> > >   generic_smp_call_function_single_interrupt+0x10/0x18
> > >   handle_IPI+0xec/0x1a8
> > >   arch_cpu_idle+0x10/0x18
> > >   do_idle+0x1d0/0x2b0
> > >   cpu_startup_entry+0x24/0x40
> > >   secondary_start_kernel+0x1b4/0x208
> > 
> > Could you investigate a bit the reason why timeout is triggered?
> 
> Yeah, it does seem a strange coincidence that the SCSI command even failed
> and we have to retry, since these should be uncommon events. I'll check on
> this LLDD error.
> 
> > 
> > Especially we suppose to drain all in-flight requests before the
> > last CPU of this hctx becomes offline, and it shouldn't be caused by
> > the hctx becoming dead, so still need you to confirm that all
> > in-flight requests are really drained in your test.
> 
> ok
> 
> Or is it still
> > possible to dispatch to LDD after BLK_MQ_S_INTERNAL_STOPPED is set?
> 
> It shouldn't be. However it would seem that this IO had been dispatched to
> the LLDD, the hctx dies, and then we attempt to requeue on that hctx.

But this patch does wait for completion of in-flight request before
shutdown the last CPU of this hctx.


Thanks,
Ming


  reply	other threads:[~2019-10-29  1:50 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-14  1:50 [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug Ming Lei
2019-10-14  1:50 ` [PATCH V4 1/5] blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED Ming Lei
2019-10-14  1:50 ` [PATCH V4 2/5] blk-mq: prepare for draining IO when hctx's all CPUs are offline Ming Lei
2019-10-14  1:50 ` [PATCH V4 3/5] blk-mq: stop to handle IO and drain IO before hctx becomes dead Ming Lei
2019-11-28  9:29   ` John Garry
2019-10-14  1:50 ` [PATCH V4 4/5] blk-mq: re-submit IO in case that hctx is dead Ming Lei
2019-10-14  1:50 ` [PATCH V4 5/5] blk-mq: handle requests dispatched from IO scheduler " Ming Lei
2019-10-16  8:58 ` [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug John Garry
2019-10-16 12:07   ` Ming Lei
2019-10-16 16:19     ` John Garry
     [not found]       ` <55a84ea3-647d-0a76-596c-c6c6b2fc1b75@huawei.com>
2019-10-20 10:14         ` Ming Lei
2019-10-21  9:19           ` John Garry
2019-10-21  9:34             ` Ming Lei
2019-10-21  9:47               ` John Garry
2019-10-21 10:24                 ` Ming Lei
2019-10-21 11:49                   ` John Garry
2019-10-21 12:53                     ` Ming Lei
2019-10-21 14:02                       ` John Garry
2019-10-22  0:16                         ` Ming Lei
2019-10-22 11:19                           ` John Garry
2019-10-22 13:45                             ` Ming Lei
2019-10-25 16:33             ` John Garry
2019-10-28 10:42               ` Ming Lei
2019-10-28 11:55                 ` John Garry
2019-10-29  1:50                   ` Ming Lei [this message]
2019-10-29  9:22                     ` John Garry
2019-10-29 10:05                       ` Ming Lei
2019-10-29 17:54                         ` John Garry
2019-10-31 16:28                         ` John Garry
2019-11-28  1:09 ` chenxiang (M)
2019-11-28  2:02   ` Ming Lei
2019-11-28 10:45     ` John Garry

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