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From: John Garry <john.garry@huawei.com>
To: Ming Lei <ming.lei@redhat.com>,
	"chenxiang (M)" <chenxiang66@hisilicon.com>
Cc: Jens Axboe <axboe@kernel.dk>, <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: Thu, 28 Nov 2019 10:45:49 +0000	[thread overview]
Message-ID: <3c0d8630-8774-809e-47b1-bf71e51834f0@huawei.com> (raw)
In-Reply-To: <20191128020205.GB3277@ming.t460p>

On 28/11/2019 02:02, Ming Lei wrote:
> On Thu, Nov 28, 2019 at 09:09:13AM +0800, chenxiang (M) wrote:
>> Hi,
>>
>> 在 2019/10/14 9:50, Ming Lei 写道:
>>> Hi,
>>>
>>> Thomas mentioned:
>>>       "
>>>        That was the constraint of managed interrupts from the very beginning:
>>>         The driver/subsystem has to quiesce the interrupt line and the associated
>>>         queue _before_ it gets shutdown in CPU unplug and not fiddle with it
>>>         until it's restarted by the core when the CPU is plugged in again.
>>>       "
>>>
>>> But no drivers or blk-mq do that before one hctx becomes dead(all
>>> CPUs for one hctx are offline), and even it is worse, blk-mq stills tries
>>> to run hw queue after hctx is dead, see blk_mq_hctx_notify_dead().
>>>
>>> This patchset tries to address the issue by two stages:
>>>
>>> 1) add one new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE
>>>
>>> - mark the hctx as internal stopped, and drain all in-flight requests
>>> if the hctx is going to be dead.
>>>
>>> 2) re-submit IO in the state of CPUHP_BLK_MQ_DEAD after the hctx becomes dead
>>>
>>> - steal bios from the request, and resubmit them via generic_make_request(),
>>> then these IO will be mapped to other live hctx for dispatch
>>>
>>> Please comment & review, thanks!
>>>
>>> John, I don't add your tested-by tag since V3 have some changes,
>>> and I appreciate if you may run your test on V3.
>>
>> I tested those patchset with John's testcase, except dump_stack() in
>> function __blk_mq_run_hw_queue() sometimes occurs  which don't
>> affect the function, it solves the CPU hotplug issue, so add tested-by for
>> those patchset:
>>
>> Tested-by: Xiang Chen <chenxiang66@hisilicon.com>
> 
> Thanks for your test.

So I had to give up testing as my board experienced some SCSI timeout 
even without hotplugging or including this patchset.

FWIW, I did test NVMe successfully though.

> 
> I plan to post a new version for 5.6 cycle, and there is still some
> small race window related with requeue to be covered.
> 

thanks!

> Thanks,
> Ming
> 
> .
> 


      reply	other threads:[~2019-11-28 10:46 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-14  1:50 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
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 [this message]

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