High cache usage with Influxdb 1.7

Below is the cache usage of my system in G, I am not sure why it is taking up too much cache, is there way I can restrict this.
index version is already set to tsi1

free -g -w
total used free shared buffers cache available
Mem: 251 37 1 4 0 211 221
Swap: 0 0 0

Version - influxdb 1.7
index-version = “tsi1”
cache-max-memory-size = “4g”