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From: John Garry <john.garry@huawei.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>,
	<linux-block@vger.kernel.org>, <linux-scsi@vger.kernel.org>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Jens Axboe <axboe@kernel.dk>,
	Douglas Gilbert <dgilbert@interlog.com>,
	Hannes Reinecke <hare@suse.com>
Subject: Re: [bug report] shared tags causes IO hang and performance drop
Date: Wed, 7 Jul 2021 18:06:08 +0100	[thread overview]
Message-ID: <ddb65e36-28e8-b5ff-9ae9-37fe3d455acb@huawei.com> (raw)
In-Reply-To: <YIfe+mpcV17XsHuL@T590>

On 27/04/2021 10:52, Ming Lei wrote:
>>> Then you just waste lots of memory, I remember that scsi request payload
>>> is a bit big.
>> It's true that we waste much memory for regular static requests for when
>> using hostwide tags today.
>>
>> One problem in trying to use a single set of "hostwide" static requests is
>> that we call blk_mq_init_request(..., hctx_idx, ...) ->
>> set->ops->init_request(.., hctx_idx, ...) for each static rq, and this would
>> not work for a single set of "hostwide" requests.
>>
>> And I see a similar problem for a "request queue-wide" sched static
>> requests.
>>
>> Maybe we can improve this in future.
> OK, fair enough.
> 

JFYI, I am working on this now.

My idea is to introduce a hostwide and request-wide static requests (for 
hostwide tagset), and have the per-hctx tags point at them, so that we 
don't need to allocate per-hctx static requests.

SCSI init_request callback just ignores hctx_idx passed, so then we can 
just call init_request(hctx_idx = 0) for those hostwide/request 
queue-wide static requests.

Thanks,
John


  parent reply	other threads:[~2021-07-07 17:13 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-14  7:50 [bug report] shared tags causes IO hang and performance drop Ming Lei
2021-04-14 10:10 ` John Garry
2021-04-14 10:38   ` Ming Lei
2021-04-14 10:42   ` Kashyap Desai
2021-04-14 11:12     ` Ming Lei
2021-04-14 12:06       ` John Garry
2021-04-15  3:46         ` Ming Lei
2021-04-15 10:41           ` John Garry
2021-04-15 12:18             ` Ming Lei
2021-04-15 15:41               ` John Garry
2021-04-16  0:46                 ` Ming Lei
2021-04-16  8:29                   ` John Garry
2021-04-16  8:39                     ` Ming Lei
2021-04-16 14:59                       ` John Garry
2021-04-20  3:06                         ` Douglas Gilbert
2021-04-20  3:22                           ` Bart Van Assche
2021-04-20  4:54                             ` Douglas Gilbert
2021-04-20  6:52                               ` Ming Lei
2021-04-20 20:22                                 ` Douglas Gilbert
2021-04-21  1:40                                   ` Ming Lei
2021-04-23  8:43           ` John Garry
2021-04-26 10:53             ` John Garry
2021-04-26 14:48               ` Ming Lei
2021-04-26 15:52                 ` John Garry
2021-04-26 16:03                   ` Ming Lei
2021-04-26 17:02                     ` John Garry
2021-04-26 23:59                       ` Ming Lei
2021-04-27  7:52                         ` John Garry
2021-04-27  9:11                           ` Ming Lei
2021-04-27  9:37                             ` John Garry
2021-04-27  9:52                               ` Ming Lei
2021-04-27 10:15                                 ` John Garry
2021-07-07 17:06                                 ` John Garry [this message]
2021-04-14 13:59       ` Kashyap Desai
2021-04-14 17:03         ` Douglas Gilbert
2021-04-14 18:19           ` John Garry
2021-04-14 19:39             ` Douglas Gilbert
2021-04-15  0:58         ` Ming Lei

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