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

On Wed, Oct 30, 2024 at 05:57:08PM +0100, Christoph Hellwig wrote:

quoted

On Wed, Oct 30, 2024 at 04:50:52PM +0100, Christoph Hellwig wrote:

quoted

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.
 

quoted

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.