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From: Ming Lei <ming.lei@redhat.com>
To: "chenxiang (M)" <chenxiang66@hisilicon.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, John Garry <john.garry@huawei.com>,
	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 10:02:05 +0800	[thread overview]
Message-ID: <20191128020205.GB3277@ming.t460p> (raw)
In-Reply-To: <b3d90798-484f-09f5-a22f-f3ed3701f0d4@hisilicon.com>

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.

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,
Ming


  reply	other threads:[~2019-11-28  2:02 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 [this message]
2019-11-28 10:45     ` John Garry

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