The following pattern indicates that your system will benefit from increasing CMS Cache limit or/and CMS DB clean-up.
It means CMS loads new objects from CMS DB and purges old ones because the cache limit is exceeded.
Problem severity can be seen in the frequency and duration of such cycles.
The perfect picture is when you don’t see spikes or even when cache size doesn’t reach its limit, though there is no need to pursue it.
SAP Note: 1981894 – "Number of Objects in CMS System Cache"