Re: [PATCH] scsi: associate bio write hint with WRITE CDB

From: Randall Huang
Date: Fri Jan 04 2019 - 00:23:04 EST

On Thu, Jan 03, 2019 at 11:57:38PM -0500, Martin K. Petersen wrote:
> Ewan,
> > SBC-5 says that support for the grouping function is indicated by the
> > GROUP_SUP bit in the Extended Inquiry VPD page (86h). I'm not sure
> > how many devices actually support that page though. Probably most
> > don't.
> Several devices support it, albeit for various different purposes. It's
> one of these wonderful features whose interpretation was left outside
> the scope of the spec for a long time.
> So even though we absolutely and positively need to make setting GROUP
> NUMBER conditional on GROUP_SUP being reported, we also need additional
> information from the storage about how the field should be interpreted.
> The official way to report hinting is for the device to implement the IO
> Advice Hints Grouping mode page. I wrote some code to support that but
> no vendors that I know of ended up actually shipping an implementation.
> A few implemented my older I/O class proposal but didn't ship that
> either despite really convincing performance results.
> If Randall has access to a device which implements hinting, I'd love to
> know more.
I am working on Android phone.
The idea is to enable write hint for Turbo write UFS feature.
Turbo write feature in UFS 3.x is under discussion in JEDEC JC-64.
This patch is the under-lying framework for supporting this feature.
> --
> Martin K. Petersen Oracle Linux Engineering