linux-kernel - Re: [PATCH v8 00/18] blk-mq/scsi: Provide hostwide shared tags for SCSI HBAs

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Date:   Fri, 4 Sep 2020 10:09:27 +0100
From:   John Garry <john.garry@...wei.com>
To:     Jens Axboe <axboe@...nel.dk>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <don.brace@...rosemi.com>,
        <kashyap.desai@...adcom.com>, <ming.lei@...hat.com>,
        <bvanassche@....org>, <dgilbert@...erlog.com>,
        <paolo.valente@...aro.org>, <hare@...e.de>, <hch@....de>
CC:     <sumit.saxena@...adcom.com>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <esc.storagedev@...rosemi.com>, <megaraidlinux.pdl@...adcom.com>,
        <chenxiang66@...ilicon.com>, <luojiaxing@...wei.com>
Subject: Re: [PATCH v8 00/18] blk-mq/scsi: Provide hostwide shared tags for
 SCSI HBAs

On 03/09/2020 22:23, Jens Axboe wrote:
> On 8/19/20 9:20 AM, John Garry wrote:
>> Hi all,
>>
>> Here is v8 of the patchset.
>>
>> In this version of the series, we keep the shared sbitmap for driver tags,
>> and introduce changes to fix up the tag budgeting across request queues.
>> We also have a change to count requests per-hctx for when an elevator is
>> enabled, as an optimisation. I also dropped the debugfs changes - more on
>> that below.
>>
>> Some performance figures:
>>
>> Using 12x SAS SSDs on hisi_sas v3 hw. mq-deadline results are included,
>> but it is not always an appropriate scheduler to use.
>>
>> Tag depth 		4000 (default)			260**
>>
>> Baseline (v5.9-rc1):
>> none sched:		2094K IOPS			513K
>> mq-deadline sched:	2145K IOPS			1336K
>>
>> Final, host_tagset=0 in LLDD *, ***:
>> none sched:		2120K IOPS			550K
>> mq-deadline sched:	2121K IOPS			1309K
>>
>> Final ***:
>> none sched:		2132K IOPS			1185			
>> mq-deadline sched:	2145K IOPS			2097	
>>
>> * this is relevant as this is the performance in supporting but not
>>    enabling the feature
>> ** depth=260 is relevant as some point where we are regularly waiting for
>>     tags to be available. Figures were are a bit unstable here.
>> *** Included "[PATCH V4] scsi: core: only re-run queue in
>>      scsi_end_request() if device queue is busy"
>>
>> A copy of the patches can be found here:
>> https://github.com/hisilicon/kernel-dev/tree/private-topic-blk-mq-shared-tags-v8
>>
>> The hpsa patch depends on:
>> https://lore.kernel.org/linux-scsi/20200430131904.5847-1-hare@suse.de/
>>
>> And the smartpqi patch is not to be accepted.
>>
>> Comments (and testing) welcome, thanks!
> 
> I applied 1-11, leaving the SCSI core bits and drivers to Martin. I can
> also carry them, just let me know.
> 

Great, thanks!

So the SCSI parts depend on the block parts for building, so I guess it 
makes sense if you could carry them also.

hpsa and smartpqi patches are pending for now, but the rest could be 
picked up. Martin/James may want more review of the SCSI core bits, though.

Thanks again,
John