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
next prev 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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