RHEL 7.4, heavy workload(s) and SWAP usage

This might not be the correct board for this, but since I'm a DBA and I'll ask here. I have several RHEL 7.4 servers, running a mix of MariaDB (10.1, 10.2) and MongoDB (3.4). The problem was happening with RHEL 7.3 as well. All of these servers have 256Gb of memory with local SSD array storage, and even given heavy workloads the highest active memory-in-use footprint is less than 100Gb at any one time. I've been profiling this for quite some time: On each of these servers, even though there is always plenty of free memory available, the systems are incrementally going into swap. I've tried setting the vm.swappiness value to 1, but incremental jumps of swap are still happening. Is this happening to anyone else? Does anyone know, with a large amount of memory available, if setting swappiness to 0 has ill effects? Thanks