But if you think this has a better home, I'm assuming that the guys
will be open to that.
Also see the reply from Ming. It's a balancing act - don't want to add
extra overhead to the core, but also don't want to carry an extra
scheduler if the main change is really just variable dispatch batching.
And since we already have a notion of that, seems worthwhile to explore
that venue.
I agree,
The main difference is that this balancing is not driven from device
resource pressure, but rather from an assumption of device specific
optimization (and also with a specific optimization target), hence a
scheduler a user would need to opt-in seemed like a good compromise.
But maybe Ming has some good ideas on a different way to add it..
So here's another case - virtualized nvme. The commit overhead is
suitably large there that performance suffers quite a bit, similarly to
your remote storage case. If we had suitable logic in the core, then we
could easily propagate this knowledge when setting up the queue. Then it
could happen automatically, without needing a configuration to switch to
a specific scheduler.
Yes, these use-cases share characteristics. I'm not at all opposed to
placing this in the core. I do think that in order to put something like
this in the core, the bar needs to be higher such that an optimization
target cannot be biased towards a workload (i.e. needs to be adaptive).
I'm still not sure how we would build this on top of what we already
have as it is really centered around device being busy (which is not
the case for nvme), but I didn't put enough thought into it yet.
