Use the following search with a column chart visualisation. It will give you a good overview of what Splunk processes use the most memory:

index=_introspection sourcetype=splunk_resource_usage component=PerProcess host=* | eval process = 'data.process' | eval args = 'data.args' | eval sid = 'data.search_props.sid' | eval elapsed = 'data.elapsed' | eval mem_used = 'data.mem_used' | eval mem = 'data.mem' | eval pct_memory = 'data.pct_memory' | eval app = 'data.search_props.app' | eval type = 'data.search_props.type' | eval mode = 'data.search_props.mode' | eval user = 'data.search_props.user' | eval role = 'data.search_props.role' | eval process_class = case( process=="splunk-optimize","index service", process=="sh" OR process=="ksh" OR process=="bash" OR like(process,"python%") OR process=="powershell","scripted input", process=="mongod", "KVStore") | eval process_class = case( process=="splunkd" AND (like(args,"-p %start%") OR like(args,"service")),"splunkd server", process=="splunkd" AND isnotnull(sid),"search", process=="splunkd" AND (like(args,"fsck%") OR like(args,"recover-metadata%") OR like(args,"cluster_thing")),"index service", process=="splunkd" AND args=="instrument-resource-usage", "scripted input", (like(process,"python%") AND like(args,"%/appserver/mrsparkle/root.py%")) OR like(process,"splunkweb"),"Splunk Web", isnotnull(process_class), process_class) | eval process_class = if(isnull(process_class),"other",process_class) | stats latest(data.mem_used) AS resource_usage_dedup latest(process_class) AS process_class by data.pid, _time | stats sum(resource_usage_dedup) AS resource_usage by _time, process_class | timechart minspan=10s median(resource_usage) AS "Resource Usage" by process_class