From: John Garry <john.garry@huawei.com>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: <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 V3 0/5] blk-mq: improvement on handling IO during CPU hotplug
Date: Tue, 8 Oct 2019 10:06:26 +0100 [thread overview]
Message-ID: <bf9687ef-4a90-73f7-3028-4c5d56c8d66b@huawei.com> (raw)
In-Reply-To: <20191008041821.2782-1-ming.lei@redhat.com>
On 08/10/2019 05:18, Ming Lei wrote:
> 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.
>
Will do, Thanks
> V3:
> - re-organize patch 2 & 3 a bit for addressing Hannes's comment
> - fix patch 4 for avoiding potential deadlock, as found by Hannes
>
> V2:
> - patch4 & patch 5 in V1 have been merged to block tree, so remove
> them
> - addres
next prev parent reply other threads:[~2019-10-08 9:06 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 4:18 [PATCH V3 0/5] blk-mq: improvement on handling IO during CPU hotplug Ming Lei
2019-10-08 4:18 ` [PATCH V3 1/5] blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED Ming Lei
2019-10-08 4:18 ` [PATCH V3 2/5] blk-mq: prepare for draining IO when hctx's all CPUs are offline Ming Lei
2019-10-08 4:18 ` [PATCH V3 3/5] blk-mq: stop to handle IO and drain IO before hctx becomes dead Ming Lei
2019-10-08 17:03 ` John Garry
2019-10-08 4:18 ` [PATCH V3 4/5] blk-mq: re-submit IO in case that hctx is dead Ming Lei
2019-10-08 4:18 ` [PATCH V3 5/5] blk-mq: handle requests dispatched from IO scheduler " Ming Lei
2019-10-08 9:06 ` John Garry [this message]
2019-10-08 17:15 ` [PATCH V3 0/5] blk-mq: improvement on handling IO during CPU hotplug John Garry
2019-10-09 8:39 ` Ming Lei
2019-10-09 8:49 ` John Garry
2019-10-10 10:30 ` Ming Lei
2019-10-10 11:21 ` John Garry
2019-10-11 8:51 ` John Garry
2019-10-11 11:55 ` Ming Lei
2019-10-11 14:10 ` John Garry
2019-10-14 1:25 ` Ming Lei
2019-10-14 8:29 ` John Garry
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