On 09/21, Matthew Wilcox wrote:

On Thu, Sep 21, 2023 at 12:39:00PM -0700, Bart Van Assche wrote:

quoted

On 9/21/23 12:27, Matthew Wilcox wrote:

quoted

On Thu, Sep 21, 2023 at 07:27:08AM -0700, Bart Van Assche wrote:

quoted

On 9/21/23 00:46, Niklas Cassel wrote:

quoted

Should NVMe streams be brought back? Yes? No?

From commit 561593a048d7 ("Merge tag 'for-5.18/write-streams-2022-03-18'
of git://git.kernel.dk/linux-block"): "This removes the write streams
support in NVMe. No vendor ever really shipped working support for this,
and they are not interested in supporting it."

It sounds like UFS is at the same stage that NVMe got to -- standard
exists, no vendor has committed to actually shipping it.  Isn't bringing
it back a little premature?

Hi Matthew,

That's a misunderstanding. UFS vendors support interpreting the SCSI GROUP
NUMBER as a data temperature since many years, probably since more than ten
years. Additionally, for multiple UFS vendors having the data temperature
available is important for achieving good performance. This message shows
how UFS vendors were using that information before write hint support was
removed: https://lore.kernel.org/linux-block/PH0PR08MB7889642784B2E1FC1799A828DB0B9@PH0PR08MB7889.namprd08.prod.outlook.com/ (local)

If vendor support already exists, then why did you dodge the question
asking for quantified data that I asked earlier?  And can we have that
data now?

I'm in doubt this patch-set really requires the quantified data which may be
mostly confidential to all the companies, also given the revert reason was no
user, IIUC. OTOH, I'm not sure whether you're famailiar with FTL, but, when
we consider the entire stack ranging from f2fs to FTL which manages NAND blocks,
I do see a clear benefit to give the temperature hints for FTL to align therein
garbage collection unit with one in f2fs, which is the key idea on Zoned UFS
in mobile world, I believe. Otherwise, it can show non-deterministic longer
write latencies due to internal GCs, increase WAI feeding to shorter lifetime.