Improve verifier scaling algorithm

[rphmeier]

@keorn suggested a PID controller, but it seems a bit overkill. Somewhere in the middle of current complexity and that would be nice.

Update time should also be reduced, once a minute is far too long.

[5chdn]

This optimization labelled issue is inactive since last year.

@paritytech/core-devs Please, confirm within 7 days if this is still relevant. If so, please comment below and add an assignee, or close it otherwise.

[rphmeier]

yes, i'd say it's still relevant. will probably revisit it fairly soon, but have been focusing on other things.

[folsen]

I can't really even make out what this means, @rphmeier if you have a more specific proposal that someone else could pick up, please reopen with that description.

[rphmeier]

This is about the --scale-verifiers flag which activates threads for parallel ethash verification dynamically.

[folsen]

Reopening as it might actually be some amount of boost in performance if we could parallelise more/better.

[debris]

I'm closing as this is not a priority right now and will not be in a foreseeable future