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From: John Garry <john.garry@huawei.com>
To: Ming Lei <ming.lei@redhat.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 V3 0/5] blk-mq: improvement on handling IO during CPU hotplug
Date: Thu, 10 Oct 2019 12:21:39 +0100	[thread overview]
Message-ID: <41b9185d-f780-f08f-dd63-9ad02a6976d4@huawei.com> (raw)
In-Reply-To: <20191010103016.GA22976@ming.t460p>

On 10/10/2019 11:30, Ming Lei wrote:
>> Yes, hisi_sas. So, right, it is single queue today on mainline, but I
>> > manually made it multiqueue on my dev branch just to test this series.
>> > Otherwise I could not test it for that driver.
>> >
>> > My dev branch is here, if interested:
>> > https://github.com/hisilicon/kernel-dev/commits/private-topic-sas-5.4-mq
> Your conversion shouldn't work given you do not change .can_queue in the
> patch of 'hisi_sas_v3: multiqueue support'.

Ah, I missed that, but I don't think that it will make a difference 
really since I'm only using a single disk, so I don't think that 
can_queue really comes into play. But....

>
> As discussed before, tags of hisilicon V3 is HBA wide. If you switch
> to real hw queue, each hw queue has to own its independent tags.
> However, that isn't supported by V3 hardware.

I am generating the tag internally in the driver now, so that hostwide 
tags issue should not be an issue.

And, to be clear, I am not paying too much attention to performance, but 
rather just hotplugging while running IO.

An update on testing:
I did some scripted overnight testing. The script essentially loops like 
this:
- online all CPUS
- run fio binded on a limited bunch of CPUs to cover a hctx mask for 1 
minute
- offline those CPUs
- wait 1 minute (> SCSI or NVMe timeout)
- and repeat

SCSI is actually quite stable, but NVMe isn't. For NVMe I am finding 
some fio processes never dying with IOPS @ 0. I don't see any NVMe 
timeout reported. Did you do any NVMe testing of this sort?

Thanks,
John

>
> See previous discussion:
>
> https://marc.info/?t=155928863000001&r=1&w=2
>
>
> Thanks,
> Ming
>
> .
>



  reply	other threads:[~2019-10-10 11:21 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 ` [PATCH V3 0/5] blk-mq: improvement on handling IO during CPU hotplug John Garry
2019-10-08 17:15   ` 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 [this message]
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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