Re: [PATCH 00/13] Pass data temperature information to zoned UFS devices

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On Wed, Sep 20, 2023 at 01:46:41PM -0700, Bart Van Assche wrote:
> On 9/20/23 12:28, Matthew Wilcox wrote:
> > On Wed, Sep 20, 2023 at 12:14:25PM -0700, Bart Van Assche wrote:
> > > Zoned UFS vendors need the data temperature information. Hence
> > > this patch series that restores write hint information in F2FS and
> > > in the block layer. The SCSI disk (sd) driver is modified such that
> > > it passes write hint information to SCSI devices via the GROUP
> > > NUMBER field.
> > 
> > "Need" in what sense?  Can you quantify what improvements we might see
> > from this patchset?
> Hi Matthew,
> This is what Jens wrote about 1.5 years ago in reply to complaints about
> the removal of write hint support making it impossible to pass write hint
> information to SSD devices: "If at some point there's a
> desire to actually try and upstream this support, then we'll be happy to
> review that patchset."
> (
> Hence this patch series.
> Recently T10 standardized how data temperature information should be passed
> to SCSI devices. One of the patches in this series translates write hint
> information into a data temperature for SCSI devices. This can be used by
> SCSI SSD devices (including UFS devices) to reduce write amplification
> inside the device because host software should assign the same data
> temperature to all data that will be garbage collected at once.

Hello Bart,

Considering that this API (F_GET_FILE_RW_HINT / F_SET_FILE_RW_HINT)
was previously only used by NVMe (NVMe streams).

Yet, this API and the support in NVMe (NVMe streams) was removed.

Now you want to re-add the same API, but this time, it will only
be used by SCSI.

Since you basically revert (some of) the patches, I would have expected
the cover letter to at least mention NVMe somewhere.

Should NVMe streams be brought back? Yes? No?
While I have a strong guess of what the NVMe maintainers will say, I think
that your cover letter should mention "why"/"why not" the NVMe support
"is"/"is not" reverted.

Kind regards,

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