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From: Ming Lei <ming.lei@redhat.com>
To: Hannes Reinecke <hare@suse.de>
Cc: John Garry <john.garry@huawei.com>,
	don.brace@microsemi.com, axboe@kernel.dk, jejb@linux.ibm.com,
	martin.petersen@oracle.com, kashyap.desai@broadcom.com,
	sumit.saxena@broadcom.com, bvanassche@acm.org, hare@suse.com,
	hch@lst.de, shivasharan.srikanteshwara@broadcom.com,
	linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	esc.storagedev@microsemi.com, chenxiang66@hisilicon.com,
	megaraidlinux.pdl@broadcom.com
Subject: Re: [PATCH RFC v7 12/12] hpsa: enable host_tagset and switch to MQ
Date: Tue, 14 Jul 2020 18:44:37 +0800	[thread overview]
Message-ID: <20200714104437.GB602708@T590> (raw)
In-Reply-To: <799af415-cb02-278e-1af2-c6179a94a8a8@suse.de>

On Tue, Jul 14, 2020 at 12:19:07PM +0200, Hannes Reinecke wrote:
> On 7/14/20 11:53 AM, John Garry wrote:
> > On 14/07/2020 09:06, Ming Lei wrote:
> >>> v7 is here:
> >>>
> >>> https://github.com/hisilicon/kernel-dev/commits/private-topic-blk-mq-shared-tags-rfc-v7
> >>>
> >>>
> >>> So that should be good to test with for now.
> >>>
> >>> And I was going to ask this same question about smartpqi, so can you
> >>> please
> >>> let me know about this one?
> > 
> > Hi Ming,
> > 
> >> smartpqi is real MQ HBA, do you need any change wrt. shared tags?
> > 
> > Is it really?
> > 
> > As I see, today it maintains a single tagset per HBA. So Hannes' change
> > in this series seems ok. However, I do worry that mainline code may be
> > wrong, as block layer may send can_queue * nr_hw_queues requests, when
> > it seems the HBA can only handle can_queue requests.
> > 
> Correct. There is only one tagset per host, even if the host supports
> several queues (guess why it's called smart PQI :-).
> And mainline code isn't really wrong, it just allocates the next free
> tag from the host tagset; it's not using the block-layer tags at all.
> Precisely because the block layer currently cannot guarantee that tags
> are unique per host.

OK, pqi_alloc_io_request() does the real tag allocation, which looks a
very bad implementation, cause the real tags can be used up easily.

In my machine, there are 32 queues(32 cpu cores), each queue has 1013
tags, so there can be 32*1013 requests coming from block layer, meantime
smartpqi can only handles 1013 requests. I guess it isn't hard to
trigger softlock by running heavy/concurrent smartpqi IO.

> 
> And the point of this patchset is exactly that the block layer will only
> send up to 'can_queue' requests, irrespective on how many hardware
> queues are present.

That is only true for shared tags.

Thanks,
Ming


  parent reply	other threads:[~2020-07-14 10:45 UTC|newest]

Thread overview: 123+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-10 17:29 [PATCH RFC v7 00/12] blk-mq/scsi: Provide hostwide shared tags for SCSI HBAs John Garry
2020-06-10 17:29 ` [PATCH RFC v7 01/12] blk-mq: rename BLK_MQ_F_TAG_SHARED as BLK_MQ_F_TAG_QUEUE_SHARED John Garry
2020-06-10 17:29 ` [PATCH RFC v7 02/12] blk-mq: rename blk_mq_update_tag_set_depth() John Garry
2020-06-11  2:57   ` Ming Lei
2020-06-11  8:26     ` John Garry
2020-06-23 11:25       ` John Garry
2020-06-23 14:23         ` Hannes Reinecke
2020-06-24  8:13           ` Kashyap Desai
2020-06-29 16:18             ` John Garry
2020-08-10 16:51           ` Kashyap Desai
2020-08-11  8:01             ` John Garry
2020-08-11 16:34               ` Kashyap Desai
2020-06-10 17:29 ` [PATCH RFC v7 03/12] blk-mq: Use pointers for blk_mq_tags bitmap tags John Garry
2020-06-10 17:29 ` [PATCH RFC v7 04/12] blk-mq: Facilitate a shared sbitmap per tagset John Garry
2020-06-11  3:37   ` Ming Lei
2020-06-11 10:09     ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 05/12] blk-mq: Record nr_active_requests per queue for when using shared sbitmap John Garry
2020-06-11  4:04   ` Ming Lei
2020-06-11 10:22     ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 06/12] blk-mq: Record active_queues_shared_sbitmap per tag_set " John Garry
2020-06-11 13:16   ` Hannes Reinecke
2020-06-11 14:22     ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 07/12] blk-mq: Add support in hctx_tags_bitmap_show() for a " John Garry
2020-06-11 13:19   ` Hannes Reinecke
2020-06-11 14:33     ` John Garry
2020-06-12  6:06       ` Hannes Reinecke
2020-06-29 15:32         ` About sbitmap_bitmap_show() and cleared bits (was Re: [PATCH RFC v7 07/12] blk-mq: Add support in hctx_tags_bitmap_show() for a shared sbitmap) John Garry
2020-06-30  6:33           ` Hannes Reinecke
2020-06-30  7:30             ` John Garry
2020-06-30 11:36               ` John Garry
2020-06-30 14:55           ` Bart Van Assche
2020-07-13  9:41         ` [PATCH RFC v7 07/12] blk-mq: Add support in hctx_tags_bitmap_show() for a shared sbitmap John Garry
2020-07-13 12:20           ` Hannes Reinecke
2020-06-10 17:29 ` [PATCH RFC v7 08/12] scsi: Add template flag 'host_tagset' John Garry
2020-06-10 17:29 ` [PATCH RFC v7 09/12] scsi: hisi_sas: Switch v3 hw to MQ John Garry
2020-06-10 17:29 ` [PATCH RFC v7 10/12] megaraid_sas: switch fusion adapters " John Garry
2020-07-02 10:23   ` Kashyap Desai
2020-07-06  8:23     ` John Garry
2020-07-06  8:45       ` Hannes Reinecke
2020-07-06  9:26         ` John Garry
2020-07-06  9:40           ` Hannes Reinecke
2020-07-06 19:19       ` Kashyap Desai
2020-07-07  7:58         ` John Garry
2020-07-07 14:45           ` Kashyap Desai
2020-07-07 16:17             ` John Garry
2020-07-09 19:01               ` Kashyap Desai
2020-07-10  8:10                 ` John Garry
2020-07-13  7:55                   ` Kashyap Desai
2020-07-13  8:42                     ` John Garry
2020-07-19 19:07                       ` Kashyap Desai
2020-07-20  7:23                       ` Kashyap Desai
2020-07-20  9:18                         ` John Garry
2020-07-21  1:13                         ` Ming Lei
2020-07-21  6:53                           ` Kashyap Desai
2020-07-22  4:12                             ` Ming Lei
2020-07-22  5:30                               ` Kashyap Desai
2020-07-22  8:04                                 ` Ming Lei
2020-07-22  9:32                                   ` John Garry
2020-07-23 14:07                                     ` Ming Lei
2020-07-23 17:29                                       ` John Garry
2020-07-24  2:47                                         ` Ming Lei
2020-07-28  7:54                                           ` John Garry
2020-07-28  8:45                                             ` Ming Lei
2020-07-29  5:25                                               ` Kashyap Desai
2020-07-29 15:36                                                 ` Ming Lei
2020-07-29 18:31                                                   ` Kashyap Desai
2020-08-04  8:36                                                     ` Ming Lei
2020-08-04  9:27                                                       ` Kashyap Desai
2020-08-05  8:40                                                         ` Ming Lei
2020-08-06 10:25                                                           ` Kashyap Desai
2020-08-06 13:38                                                             ` Ming Lei
2020-08-06 14:37                                                               ` Kashyap Desai
2020-08-06 15:29                                                                 ` Ming Lei
2020-08-08 19:05                                                                   ` Kashyap Desai
2020-08-09  2:16                                                                     ` Ming Lei
2020-08-10 16:38                                                                       ` Kashyap Desai
2020-08-11  8:09                                                                         ` John Garry
2020-08-04 17:00                                               ` John Garry
2020-08-05  2:56                                                 ` Ming Lei
2020-07-28  8:01                                   ` Kashyap Desai
2020-07-08 11:31         ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 11/12] smartpqi: enable host tagset John Garry
2020-07-14 13:16   ` John Garry
2020-07-14 13:31     ` John Garry
2020-07-14 18:16       ` Don.Brace
2020-07-15  7:28         ` John Garry
2020-07-14 14:02     ` Hannes Reinecke
2020-08-18  8:33       ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 12/12] hpsa: enable host_tagset and switch to MQ John Garry
2020-07-14  7:37   ` John Garry
2020-07-14  7:41     ` Hannes Reinecke
2020-07-14  7:52       ` John Garry
2020-07-14  8:06         ` Ming Lei
2020-07-14  9:53           ` John Garry
2020-07-14 10:14             ` Ming Lei
2020-07-14 10:43               ` Hannes Reinecke
2020-07-14 10:19             ` Hannes Reinecke
2020-07-14 10:35               ` John Garry
2020-07-14 10:44               ` Ming Lei [this message]
2020-07-14 10:52                 ` John Garry
2020-07-14 12:04                   ` Ming Lei
2020-08-03 20:39         ` Don.Brace
2020-08-04  9:27           ` John Garry
2020-08-04 15:18             ` Don.Brace
2020-08-05 11:21               ` John Garry
2020-08-14 21:04                 ` Don.Brace
2020-08-17  8:00                   ` John Garry
2020-08-17 18:39                     ` Don.Brace
2020-08-18  7:14                       ` Hannes Reinecke
2020-07-16 16:14     ` Don.Brace
2020-07-16 19:45     ` Don.Brace
2020-07-17 10:11       ` John Garry
2020-06-11  3:07 ` [PATCH RFC v7 00/12] blk-mq/scsi: Provide hostwide shared tags for SCSI HBAs Ming Lei
2020-06-11  9:35   ` John Garry
2020-06-12 18:47     ` Kashyap Desai
2020-06-15  2:13       ` Ming Lei
2020-06-15  6:57         ` Kashyap Desai
2020-06-16  1:00           ` Ming Lei
2020-06-17 11:26             ` Kashyap Desai
2020-06-22  6:24               ` Hannes Reinecke
2020-06-23  0:55                 ` Ming Lei
2020-06-23 11:50                   ` Kashyap Desai
2020-06-23 12:11                   ` Kashyap Desai

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