[PATCHv10 9/9] scsi: set permanent stream count in block limits

[Keith Busch]

On Wed, Oct 30, 2024 at 05:57:08PM +0100, Christoph Hellwig wrote:
> > On Wed, Oct 30, 2024 at 04:50:52PM +0100, Christoph Hellwig wrote:
> 
> > It sets temperature hints for different SST levels, which already
> > happens today. The last data point made some minor changes with
> > level-to-hint mapping.
> 
> Do you have a pointer to the changes?

The change moves levels 2 and 3 to "MEDIUM" (along with 0 and 1 already
there), 4 to "LONG", and >= 5 remain "EXTREME".

WAL continues to be "SHORT", as before.
 
> > Without FDP:
> > 
> > WAF:        2.72
> > IOPS:       1465
> > READ LAT:   2681us
> > UPDATE LAT: 3115us
> > 
> > With FDP (rocksdb unmodified):
> > 
> > WAF:        2.26
> > IOPS:       1473
> > READ LAT:   2415us
> > UPDATE LAT: 2807us
> > 
> > With FDP (with some minor rocksdb changes):
> > 
> > WAF:        1.67
> > IOPS:       1547
> > READ LAT:   1978us
> > UPDATE LAT: 2267us
> 
> Compared to the Numbers Hans presented at Plumbers for the Zoned XFS code,
> which should work just fine with FDP IFF we exposed real write streams,
> which roughly double read nad wirte IOPS and reduce the WAF to almost
> 1 this doesn't look too spectacular to be honest, but it sure it something.
> 
> I just wish we could get the real infraѕtructure instead of some band
> aid, which makes it really hard to expose the real thing because now
> it's been taken up and directly wired to a UAPI.
> one

This doesn't have to be the end placement streams development. I
fundamentally disagree that this locks anyone in to anything.