Default Cache Memory Limit

[jinlmsft]

This issue was brought to my attention by Bruno.

One of the workload that he has written doesn't cache the data as desired. Investigation found out that the default memory size of the container is set as 1024MB. So when the data set becomes large, it is not cached, causing the performance degradation.

I would like to open this issue to document the behavior. The questions are:

1. Should we raise default memory size?
2. Should we give a warning when cache is not working (if we do, how? Should we throw an exception, print out a warning, etc).