Allow setting cache size to < 1GB

[debdattabasu]

First of all, thank you for an awesome library. :)

I am running MongoRocks on memory constrained environments, where IMO RocksDB performs better than WiredTiger, which tends to freeze and hang frequently. However, I can not set the cache size to let's say 0.256GB like I can do in WiredTiger.

Is there a possibility of making this happen?

Regards
Debdatta Basu

[igorcanadi]

That's correct, looks like cacheGB is an integer. We'd just need to port something like this over: mongodb/mongo@b6397d9#diff-6a2e67ff05825f6d310e2938f3cfdd30

Interested in giving it a shot?