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

[Keith Busch]

On Thu, Oct 31, 2024 at 09:19:51AM +0100, Hans Holmberg wrote:
> On Wed, Oct 30, 2024 at 11:33 PM Keith Busch <kbusch at kernel.org> wrote:
> > That is very much apples-to-oranges. The B+ isn't on the same device
> > being evaluated for WAF, where this has all that mixed in. I think the
> > results are pretty good, all things considered.
> 
> No. The meta data IO is just 0.1% of all writes, so that we use a
> separate device for that in the benchmark really does not matter.

It's very little spatially, but they overwrite differently than other
data, creating many small holes in large erase blocks.
 
> Since we can achieve a WAF of ~1 for RocksDB on flash, why should we
> be content with another 67% of unwanted device side writes on top of
> that?
> 
> It's of course impossible to compare your benchmark figures and mine
> directly since we are using different devices, but hey, we definitely
> have an opportunity here to make significant gains for FDP if we just
> provide the right kernel interfaces.
> 
> Why shouldn't we expose the hardware in a way that enables the users
> to make the most out of it?

Because the people using this want this interface. Stalling for the last
6 months hasn't produced anything better, appealing to non-existent
vaporware to block something ready-to-go that satisfies a need right
now is just wasting everyone's time.

Again, I absolutely disagree that this locks anyone in to anything.
That's an overly dramatic excuse.