what should we consider for memory forecasting /proc/meminfo versus free-m on linux?

Hello,

I have been struggling these days to find correct memory usage which we need to show in reports for trending and server RAM forecasting. The good thing in our environment is that we have all our databases configured in OEM 12c and all the required data is already available for us in MGMT$METRIC views. I am even able to figure out the metric combination that I can use for trending purpose the query of which is below:

select target_name, target_type, column_label,ROLLUP_TIMESTAMP, AVERAGE,MINIMUM,MAXIMUM from sysman.mgmt$metric_hourly

where metric_name = 'Load' and column_label = 'Memory Utilization (%)'