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From: Ming Lei <ming.lei@redhat.com>
To: John Garry <john.garry@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Yanhui Ma <yama@redhat.com>,
	Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH] blk-mq: set default elevator as deadline in case of hctx shared tagset
Date: Wed, 7 Apr 2021 08:48:13 +0800	[thread overview]
Message-ID: <YG0BTVsCNKZHD3/T@T590> (raw)
In-Reply-To: <d081eb6a-ace7-c9b2-7374-7f05a31551a0@huawei.com>

On Tue, Apr 06, 2021 at 11:25:08PM +0100, John Garry wrote:
> On 06/04/2021 04:19, Ming Lei wrote:
> 
> Hi Ming,
> 
> > Yanhui found that write performance is degraded a lot after applying
> > hctx shared tagset on one test machine with megaraid_sas. And turns out
> > it is caused by none scheduler which becomes default elevator caused by
> > hctx shared tagset patchset.
> > 
> > Given more scsi HBAs will apply hctx shared tagset, and the similar
> > performance exists for them too.
> > 
> > So keep previous behavior by still using default mq-deadline for queues
> > which apply hctx shared tagset, just like before.
> 
> I think that there a some SCSI HBAs which have nr_hw_queues > 1 and don't
> use shared sbitmap - do you think that they want want this as well (without
> knowing it)?

I don't know but none has been used for them since the beginning, so not
an regression of shared tagset, but this one is really.



Thanks, 
Ming


  reply	other threads:[~2021-04-07  0:48 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-06  3:19 [PATCH] blk-mq: set default elevator as deadline in case of hctx shared tagset Ming Lei
2021-04-06  3:49 ` Martin K. Petersen
2021-04-06 17:54 ` Bart Van Assche
2021-04-06 22:25 ` John Garry
2021-04-07  0:48   ` Ming Lei [this message]
2021-04-07  8:04     ` John Garry
2021-04-07 10:14       ` Ming Lei
2021-04-14  8:21         ` Kashyap Desai
2021-04-14 10:48           ` Ming Lei
2021-04-08  8:36 ` Ming Lei
2021-04-08 15:57   ` Jens Axboe

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