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

[Qian Cai]

On Mon, 2020-11-02 at 20:01 +0530, Kashyap Desai wrote:
> > 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"

Yes, that also works.