Having little free memory available is not a worry on itself. The good old KPI of monitoring overall system cpu and memory doesn’t apply to XR for those reasons. Note also that All IOS XR routers have at least dual core cpu’s. Also BGP for instance “claiming” 80% in XR may be a good thing during convergence, however the overal cpu util would still not be too bad. There is no total cpu utilization as such as what IOS used to have. Generally we see the request for people using the cisco process or memory mibs to monitor XR and are flabbergasted by the massive output it generates. One process could hook the CPU in IOS, in XR similar issues don’t exist per-se. IOS XR monitoring is substantially different then classic IOS. Some more related detail to the IOS to XR comparison.
Also take note of the IOS to XR migration guide which has
In this document we're discussing the precise details of the hows and tos regarding this. However the architecture of the OS between IOS (monolithic) and XR (more like a linux kernel) is so different that the management of CPU and memory is not the same and we can't adopt the KPI's from IOS to XR. Since we all grew up with IOS I certainly recognize where that question (and concern) is coming from. Over the course of the last few months I received a lot of questions in relation to CPU and memory management in IOS-XR.