Cause of doc_values_memory_in_bytes and how to reduce?

We just recently upgraded to ES 2.3.1 from ES 1.7.3 and we had memory issues a few days later. Besides the fact that we have a lot of shards (Why is my heap usage always high?), I also noticed that the doc_values_memory_in_bytes value went up at the same time. It appears that that value is what caused us to go into memory issues.

I'm wondering what that value is since I was under the impression that doc_values was all on disk. And how can I clear that memory programmatically?

The file system will load the doc_values into the cache, that's what is eating up the memory. Elasticsearch will use doc_values, but retrieval will be faster if it doesn't actually have to hit the disk to read those values. Hope that helps.