RE: [PATCH v8 17/18] scsi: megaraid_sas: Added support for shared host tagset for cpuhotplug

[Kashyap Desai]

> On Wed, 2020-08-19 at 23:20 +0800, John Garry wrote:
> > From: Kashyap Desai <kashyap.desai@xxxxxxxxxxxx>
> >
> > Fusion adapters can steer completions to individual queues, and we now
> > have support for shared host-wide tags.
> > So we can enable multiqueue support for fusion adapters.
> >
> > Once driver enable shared host-wide tags, cpu hotplug feature is also
> > supported as it was enabled using below patchsets - commit
> > bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are
> > offline")
> >
> > Currently driver has provision to disable host-wide tags using
> > "host_tagset_enable" module parameter.
> >
> > Once we do not have any major performance regression using host-wide
> > tags, we will drop the hand-crafted interrupt affinity settings.
> >
> > Performance is also meeting the expecatation - (used both none and
> > mq-deadline scheduler)
> > 24 Drive SSD on Aero with/without this patch can get 3.1M IOPs
> > 3 VDs consist of 8 SAS SSD on Aero with/without this patch can get
> > 3.1M IOPs.
> >
> > Signed-off-by: Kashyap Desai <kashyap.desai@xxxxxxxxxxxx>
> > Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
> > Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
>
> Reverting this commit fixed an issue that Dell Power Edge R6415 server
> with
> megaraid_sas is unable to boot.

I will take a look at this. BTW, can you try keeping same PATCH but use
module parameter "host_tagset_enable =0"

Kashyap

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