Memory usage between 3.2.9-2.1 and 3.2.10-3.0

We have built a replicated sharded cluster with 3.2.9-2.1. A few days ago, we added a new 3.2.10-3.0 member for each of the replica set.
Everything seems fine, but memory usages between 3.2.9 and 3.2.10 are very different. Is there any memory improvement from 3.2.10-3.0?

The attachment:
#15.239 is 3.2.9-2.1, the other is 3.2.10-3.0.

Hi, I don’t see your picture clearly because it’s too small, but from your message I would assume that 3.2.10 is using less memory. The only thing I see in the release notes for 3.2.10 is this and it might be related:
MongoDB with WiredTiger may experience excessive memory fragmentation, leading to swapping and/or out-of-memory errors.
https://jira.mongodb.org/browse/SERVER-20306