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>,
Minwoo Im <minwoo.im.dev@gmail.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>,
chenxiang <chenxiang66@hisilicon.com>
Subject: Re: [PATCH V2 0/5] blk-mq: improvement on handling IO during CPU hotplug
Date: Wed, 2 Oct 2019 10:56:46 +0100 [thread overview]
Message-ID: <9add1de0-9135-fd1f-8fd4-de17234d8883@huawei.com> (raw)
In-Reply-To: <a2f9e930-1b9c-dc95-78f8-70df9460669d@huawei.com>
On 22/08/2019 18:39, John Garry wrote:
> On 12/08/2019 14:43, 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!
>>
>> V2:
>> - patch4 & patch 5 in V1 have been merged to block tree, so remove
>> them
>> - address comments from John Garry and Minwoo
>>
>>
>> Ming Lei (5):
>> blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED
>> blk-mq: add blk-mq flag of BLK_MQ_F_NO_MANAGED_IRQ
>> blk-mq: stop to handle IO before hctx's all CPUs become offline
>> blk-mq: re-submit IO in case that hctx is dead
>> blk-mq: handle requests dispatched from IO scheduler in case that hctx
>> is dead
>
> Hi Ming,
>
> This looks to fix the hotplug issue for me.
>
> Previously I could manufacture a scenario while running fio where I got
> IO timeouts, like this:
>
> root@(none)$ echo 0 > ./sys/devices/system/cpu/cpu0/online
> [ 296.897627] process 891 (fio) no longer affine to cpu0
> [ 296.898488] process 893 (fio) no longer affine to cpu0
> [ 296.910270] process 890 (fio) no longer affine to cpu0
> [ 296.927322] IRQ 775: no longer affine to CPU0
> [ 296.932762] CPU0: shutdown
> [ 296.935469] psci: CPU0 killed.
> root@(none)$ [ 326.971962] sas: Enter sas_scsi_recover_host busy: 61
> failed: 61
> [ 326.977978] sas: sas_scsi_find_task: aborting task 0x00000000e2cdc79b
> root@(none)$ [ 333.047964] hisi_sas_v3_hw 0000:74:02.0: internal task
> abort: timeout and not done.
> [ 333.055616] hisi_sas_v3_hw 0000:74:02.0: abort task: internal abort (-5)
> [ 333.062306] sas: sas_scsi_find_task: querying task 0x00000000e2cdc79b
> [ 333.068776] sas: sas_scsi_find_task: task 0x00000000e2cdc79b not at LU
> [ 333.075295] sas: task 0x00000000e2cdc79b is not at LU: I_T recover
> [ 333.081464] sas: I_T nexus reset for dev 5000c500a7b95a49
>
> Please notice the 30-second delay for the SCSI IO timeout.
>
> And now I don't see it; here's a sample for irq shutdown:
> root@(none)$ echo 0 > ./sys/devices/system/cpu/cpu0/online
> [ 344.608148] process 849 (fio) no longer affine to cpu0
> [ 344.608639] process 848 (fio) no longer affine to cpu0
> [ 344.609454] process 850 (fio) no longer affine to cpu0
> [ 344.643481] process 847 (fio) no longer affine to cpu0
> [ 346.213842] IRQ 775: no longer affine to CPU0
> [ 346.219712] CPU0: shutdown
> [ 346.222425] psci: CPU0 killed.
>
> Please notice the ~1.5s pause, which would be the queue draining.
>
> So FWIW:
> Tested-by: John Garry <john.garry@huawei.com>
>
> JFYI, I tested on 5.3-rc5 and cherry-picked
> https://github.com/ming1/linux/commit/0d2cd3c99bb0fe81d2c0ca5d68e02bdc4521d4d6
> and "blk-mq: add callback of .cleanup_rq".
>
> Cheers,
> John
Hi Jens,
I don't mean to be pushy, but can we consider to get these patches from
Ming merged?
As above, I tested on my SCSI driver and it works. I also tested on an
NVMe disk, and it solves the condition which generates this message:
root@(none)$ echo 0 > /sys/devices/system/cpu/cpu2/online
[ 465.635960] CPU2: shutdown
[ 465.638662] psci: CPU2 killed.
[ 111.381653] nvme nvme0: I/O 705 QID 18 timeout, completion polled
(that's on top off v5.4-rc1)
Thanks,
John
>
>>
>> block/blk-mq-debugfs.c | 2 +
next prev parent reply other threads:[~2019-10-02 9:57 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-12 13:43 [PATCH V2 0/5] blk-mq: improvement on handling IO during CPU hotplug Ming Lei
2019-08-12 13:43 ` [PATCH V2 1/5] blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED Ming Lei
2019-08-12 13:43 ` [PATCH V2 2/5] blk-mq: add blk-mq flag of BLK_MQ_F_NO_MANAGED_IRQ Ming Lei
2019-08-12 13:43 ` [PATCH V2 3/5] blk-mq: stop to handle IO before hctx's all CPUs become offline Ming Lei
2019-08-12 14:24 ` Hannes Reinecke
2019-08-12 22:24 ` Ming Lei
2019-08-12 13:43 ` [PATCH V2 4/5] blk-mq: re-submit IO in case that hctx is dead Ming Lei
2019-08-12 14:26 ` Hannes Reinecke
2019-08-12 22:30 ` Ming Lei
2019-08-12 13:43 ` [PATCH V2 5/5] blk-mq: handle requests dispatched from IO scheduler " Ming Lei
2019-08-12 13:46 ` [PATCH V2 0/5] blk-mq: improvement on handling IO during CPU hotplug Ming Lei
2019-08-12 16:21 ` John Garry
2019-08-12 22:45 ` Ming Lei
2019-08-22 17:39 ` John Garry
2019-10-02 9:56 ` John Garry [this message]
2019-10-02 14:36 ` Jens Axboe
2019-10-06 2:47 ` Ming Lei
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