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From: John Garry <john.garry@huawei.com>
To: Hannes Reinecke <hare@suse.de>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	"James Bottomley" <james.bottomley@hansenpartnership.com>,
	Ming Lei <ming.lei@redhat.com>, <linux-scsi@vger.kernel.org>,
	<linux-block@vger.kernel.org>
Subject: Re: [PATCH 04/11] blk-mq: Facilitate a shared sbitmap per tagset
Date: Wed, 4 Dec 2019 10:24:34 +0000
Message-ID: <6c8b8676-a3c7-6fd5-3b6d-c0b469c80756@huawei.com> (raw)
In-Reply-To: <5beb7d51-500e-5bda-4e46-8414fd8b64ff@suse.de>

On 03/12/2019 15:02, Hannes Reinecke wrote:
>>> +     */
>> If you don't have a shared sched bitmap - which I didn't think we needed
>> - then all we need is a simple sbitmap_queue_resize(&tagset->__bitmap_tags)
>>
>> Otherwise it's horrible to resize shared sched bitmaps...
>>
> Resizing shared sched bitmaps is done in patch 6/11.
> General idea is to move the scheduler bitmap into the request queue
> (well, actually the elevator), as this gives us a per-request_queue
> bitmap. Which is actually what we want here, as the scheduler will need
> to look at all requests, hence needing to access to the same bitmap.
> And it also gives us an easy way of resizing the sched tag bitmap, as
> then we can resize the bitmap on a per-queue basis, and leave the
> underlying tagset bitmap untouched.

OK, but I am just concerned if that is really required in this series 
and whether it is just another obstacle to getting it accepted.

Thanks,
John

> 
> [ .. ]
>>> diff --git a/block/blk-mq.h b/block/blk-mq.h
>>> index 78d38b5f2793..4c1ea206d3f4 100644
>>> --- a/block/blk-mq.h
>>> +++ b/block/blk-mq.h


  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-02 15:39 [PATCH RFC v5 00/11] blk-mq/scsi: Provide hostwide shared tags for SCSI HBAs Hannes Reinecke
2019-12-02 15:39 ` [PATCH 01/11] blk-mq: Remove some unused function arguments Hannes Reinecke
2019-12-02 15:39 ` [PATCH 02/11] blk-mq: rename BLK_MQ_F_TAG_SHARED as BLK_MQ_F_TAG_QUEUE_SHARED Hannes Reinecke
2019-12-02 15:39 ` [PATCH 03/11] blk-mq: rename blk_mq_update_tag_set_depth() Hannes Reinecke
2019-12-03 14:30   ` John Garry
2019-12-03 14:53     ` Hannes Reinecke
2019-12-02 15:39 ` [PATCH 04/11] blk-mq: Facilitate a shared sbitmap per tagset Hannes Reinecke
2019-12-03 14:54   ` John Garry
2019-12-03 15:02     ` Hannes Reinecke
2019-12-04 10:24       ` John Garry [this message]
2019-12-03 16:38     ` Bart Van Assche
2019-12-02 15:39 ` [PATCH 05/11] blk-mq: add WARN_ON in blk_mq_free_rqs() Hannes Reinecke
2019-12-02 15:39 ` [PATCH 06/11] blk-mq: move shared sbitmap into elevator queue Hannes Reinecke
2019-12-02 15:39 ` [PATCH 07/11] scsi: Add template flag 'host_tagset' Hannes Reinecke
2019-12-02 15:39 ` [PATCH 08/11] scsi: hisi_sas: Switch v3 hw to MQ Hannes Reinecke
2019-12-02 15:39 ` [PATCH 09/11] megaraid_sas: switch fusion adapters " Hannes Reinecke
2019-12-09 10:10   ` Sumit Saxena
2019-12-09 11:02     ` Hannes Reinecke
2019-12-02 15:39 ` [PATCH 10/11] smartpqi: enable host tagset Hannes Reinecke
2019-12-02 15:39 ` [PATCH 11/11] hpsa: enable host_tagset and switch to MQ Hannes Reinecke

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