[Plasma] consider cpu tuning for QuotaSwapper

Copying Matt's comments from MB-27433 regarding Plasma QuotaSwapper.

=============================

Wouldn't it be possible to use an exponential backoff here. On a system where the memory usage hasn't changed substantially for 100ms, it's not likely to change substantially in the next 100ms. If you can back this off say to something like 3s or 5s, that saves 29-49 polls which are otherwise eating CPU in the background.

Keep in mind, one use case here is that as a developer, I write some code, I run a test, then I have think time with more code writing. The current approach leads to a poor developer experience. Especially if I wanted to test with three docker images on my laptop, for instance.

Is there perhaps a notification API rather than a polling one?

=============================