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

[Jens Axboe <axboe@kernel.dk>]

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.

-- 
Jens Axboe