Make it possible to configure promotion policy separately for reads and writes #658
Description
Description
Make it possible to configure promotion policy separately for reads and writes.
Reason
For some workloads it's reasonable to promote reads and writes on different rules, e.g. when we know that each write will be a cache hit, but it doesn't necessarily apply to read, or the opposite, when we can have a workload when reads are very likely to produce cache hits, but for writes we have two separate random stream, one producing a lot of hits and the other one that does not have hits at all.
Possible future improvements
We can try to make PP cooperate with io classification, so that it will be possible to have different PP rules for different io classes. That would generalize solution proposed in this enhancement.