Re: [PATCH RFC v5 00/11] blk-mq/scsi: Provide hostwide shared tags for SCSI HBAs

[John Garry <john.garry@huawei.com>]

On 02/12/2019 15:39, Hannes Reinecke wrote:
> Hi all,
> 

JFYI, Sumit requested that we rebase this patchset for testing against 
the latest kernel - it no longer applies for 5.6-rc. I'm going to do 
that now and repost.

Thanks,
John

> here now is an updated version of the v2 patchset from John Garry,
> including the suggestions and reviews from the mailing list.
> John, apologies for hijacking your work :-)
> 
> For this version I've only added some slight modifications to Johns
> original patch (renaming variables etc); the contentious separate sbitmap
> allocation has been dropped in favour of Johns original version with pointers
> to the embedded sbitmap.
> 
> But more importantly I've reworked the scheduler tag allocation after
> discussions with Ming Lei.
> 
> Point is, hostwide shared tags can't really be resized; they surely
> cannot be increased (as it's a hardware limitation), and even decreasing
> is questionable as any modification here would affect all devices
> served by this HBA.
> 
> Scheduler tags, OTOH, can be considered as per-queue, as the I/O scheduler
> might want to look at all requests on all queues. As such the queue depth
> is distinct from the actual queue depth of the tagset.
> Seeing that it is distinct the depth can now be changed independently of
> the underlying tagset, and there's no need ever to change the tagset itself.
> 
> I've also modified megaraid_sas, smartpqi and hpsa to take advantage of
> host_tags.
> 
> Performance for megaraid_sas is on par with the original implementation,
> with the added benefit that with this we should be able to handle cpu
> hotplug properly.
> 
> Differences to v4:
> - Rework scheduler tag allocations
> - Revert back to the original implementation from John
> 
> Differences to v3:
> - Include reviews from Ming Lei
> 
> Differences to v2:
> - Drop embedded tag bitmaps
> - Do not share scheduling tags
> - Add patches for hpsa and smartpqi
> 
> Differences to v1:
> - Use a shared sbitmap, and not a separate shared tags (a big change!)
> 	- Drop request.shared_tag
> - Add RB tags
> 
> Hannes Reinecke (7):
>    blk-mq: rename blk_mq_update_tag_set_depth()
>    blk-mq: add WARN_ON in blk_mq_free_rqs()
>    blk-mq: move shared sbitmap into elevator queue
>    scsi: Add template flag 'host_tagset'
>    megaraid_sas: switch fusion adapters to MQ
>    smartpqi: enable host tagset
>    hpsa: enable host_tagset and switch to MQ
> 
> John Garry (3):
>    blk-mq: Remove some unused function arguments
>    blk-mq: Facilitate a shared sbitmap per tagset
>    scsi: hisi_sas: Switch v3 hw to MQ
> 
> Ming Lei (1):
>    blk-mq: rename BLK_MQ_F_TAG_SHARED as BLK_MQ_F_TAG_QUEUE_SHARED
> 
>   block/bfq-iosched.c                         |   4 +-
>   block/blk-mq-debugfs.c                      |  12 +--
>   block/blk-mq-sched.c                        |  22 +++++
>   block/blk-mq-tag.c                          | 140 +++++++++++++++++++++-------
>   block/blk-mq-tag.h                          |  27 ++++--
>   block/blk-mq.c                              | 104 +++++++++++++++------
>   block/blk-mq.h                              |   7 +-
>   block/blk-sysfs.c                           |   7 ++
>   block/kyber-iosched.c                       |   4 +-
>   drivers/scsi/hisi_sas/hisi_sas.h            |   3 +-
>   drivers/scsi/hisi_sas/hisi_sas_main.c       |  36 +++----
>   drivers/scsi/hisi_sas/hisi_sas_v3_hw.c      |  86 +++++++----------
>   drivers/scsi/hpsa.c                         |  44 ++-------
>   drivers/scsi/hpsa.h                         |   1 -
>   drivers/scsi/megaraid/megaraid_sas.h        |   1 -
>   drivers/scsi/megaraid/megaraid_sas_base.c   |  65 ++++---------
>   drivers/scsi/megaraid/megaraid_sas_fusion.c |  14 ++-
>   drivers/scsi/scsi_lib.c                     |   2 +
>   drivers/scsi/smartpqi/smartpqi_init.c       |  38 ++++++--
>   include/linux/blk-mq.h                      |   7 +-
>   include/linux/elevator.h                    |   3 +
>   include/scsi/scsi_host.h                    |   3 +
>   22 files changed, 380 insertions(+), 250 deletions(-)
>