Re: [PATCH RFC V2 3/3] scsi_mq: enable runtime PM

Johannes Thumshirn
2018-07-18T12:28:43Z

On Wed, Jul 18, 2018 at 08:06:10PM +0800, Ming Lei wrote:
> IMO the problem isn't related with slow or quick device, it is related with
> the system, especially when it cares about power consumption, such as
> mobile phone, or laptop or servers with lots of disks attached. And we know
> it is often to see some fast disks shipped in laptop, such as NVMe, or other
> SSD.

Yes but you're only taking locally attached devices into account.
This is very likely harmful on sd devices attached to a
SRP/FC/iSCSI/SAS Target in a SAN environment. These can be really fast
and people investing this money are likely to not like additional
performance penalties.

Furthermore I'd don't know if any array vendors actually implement
START/STOP DISK, etc..

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Johannes Thumshirn Storage
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